Time remains one of the least well-understood concepts in physics, most notably in quantum mechanics. A central goal is to find the fundamental limits of measuring time. One of the main obstacles is the fact that time is not an observable and thus has to be measured indirectly. Here, we explore these questions by introducing a model of time measurements that is complete and autonomous. Specifically, our autonomous quantum clock consists of a system out of thermal equilibrium—a prerequisite for any system to function as a clock—powered by minimal resources, namely, two thermal baths at different temperatures. Through a detailed analysis of this specific clock model, we find that the laws of thermodynamics dictate a trade-off between the amount of dissipated heat and the clock’s performance in terms of its accuracy and resolution. Our results furthermore imply that a fundamental entropy production is associated with the operation of any autonomous quantum clock, assuming that quantum machines cannot achieve perfect efficiency at finite power. More generally, autonomous clocks provide a natural framework for the exploration of fundamental questions about time in quantum theory and beyond.

%B Physical Review X %V 7 %P 031022 %U https://link.aps.org/doi/10.1103/PhysRevX.7.031022 %R 10.1103/PhysRevX.7.031022 %0 Journal Article %J Quantum %D 2017 %T Decoupling with random diagonal unitaries %A Nakata, Yoshifumi %A Hirche, Christoph %A Morgan, Ciara %A Winter, Andreas %X Yoshifumi Nakata, Christoph Hirche, Ciara Morgan, and Andreas Winter, Quantum 1, 18 (2017). https://doi.org/10.22331/q-2017-07-21-18 We investigate decoupling, one of the most important primitives in quantum Shannon theory, by replacing the uniformly distributed random unitaries commonly used to achieve the protocol, with… %B Quantum %V 1 %P 18 %8 jul %U https://quantum-journal.org/papers/q-2017-07-21-18/ %R 10.22331/q-2017-07-21-18 %0 Journal Article %J Physical Review Letters %D 2017 %T Discrimination Power of a Quantum Detector %A Hirche, Christoph %A Hayashi, Masahito %A Bagan, Emilio %A Calsamiglia, John %B Physical Review Letters %V 118 %8 Jan-04-2017 %U http://link.aps.org/doi/10.1103/PhysRevLett.118.160502http://harvest.aps.org/v2/journals/articles/10.1103/PhysRevLett.118.160502/fulltexthttp://link.aps.org/article/10.1103/PhysRevLett.118.160502 %! Phys. Rev. Lett. %R 10.1103/PhysRevLett.118.160502 %0 Journal Article %J PHYSICAL REVIEW X %D 2017 %T Efficient Quantum Pseudorandomness with Nearly Time-Independent Hamiltonian Dynamics %A Nakata, Yoshifumi %A Hirche, Christoph %A Koashi, Masato %A Winter, Andreas %XQuantum randomness is an essential key to understanding the dynamics of complex many-body systems and also a powerful tool for quantum engineering. However, exact realizations of quantum randomness take an extremely long time and are infeasible in many-body systems, leading to the notion of quantum pseudorandomness, also known as unitary designs. Here, to explore microscopic dynamics of generating quantum pseudorandomness in many-body systems, we provide new efficient constructions of unitary designs and propose a design Hamiltonian, a random Hamiltonian of which dynamics always forms a unitary design after a threshold time. The new constructions are based on the alternate applications of random potentials in the generalized position and momentum spaces, and we provide explicit quantum circuits generating quantum pseudorandomness significantly more efficient than previous ones. We then provide a design Hamiltonian in disordered systems with periodically changing spin-glass-type interactions. The design Hamiltonian generates quantum pseudorandomness in a constant time even in the system composed of a large number of spins. We also point out the close relationship between the design Hamiltonian and quantum chaos.

%B PHYSICAL REVIEW X %V 7 %8 apr %R 10.1103/PhysRevX.7.021006 %0 Journal Article %J PHYSICAL REVIEW A %D 2017 %T Enhancement of low-temperature thermometry by strong coupling %A Correa, Luis A. %A Perarnau-Llobet, Marti %A Hovhannisyan, Karen V. %A Hernandez-Santana, Senaida %A Mehboudi, Mohammad %A Sanpera, Anna %X We consider the problem of estimating the temperature T of a very cold equilibrium sample. The temperature estimates are drawn from measurements performed on a quantum Brownian probe strongly coupled to it. We model this scenario by resorting to the canonical Caldeira-Leggett Hamiltonian and find analytically the exact stationary state of the probe for arbitrary coupling strength. In general, the probe does not reach thermal equilibrium with the sample, due to their nonperturbative interaction. We argue that this is advantageous for low-temperature thermometry, as we show in our model that (i) the thermometric precision at low T can be significantly enhanced by strengthening the probe-sampling coupling, (ii) the variance of a suitable quadrature of our Brownian thermometer can yield temperature estimates with nearly minimal statistical uncertainty, and (iii) the spectral density of the probe-sample coupling may be engineered to further improve thermometric performance. These observations may find applications in practical nanoscale thermometry at low temperatures-a regime which is particularly relevant to quantum technologies. %B PHYSICAL REVIEW A %V 96 %R 10.1103/PhysRevA.96.062103 %0 Journal Article %J IEEE Transactions on Information Theory %D 2017 %T From Log-Determinant Inequalities to Gaussian Entanglement via Recoverability Theory %A Lami, Ludovico %A Hirche, Christoph %A Adesso, Gerardo %A Winter, Andreas %B IEEE Transactions on Information Theory %V 63 %P 7553 - 7568 %8 Jan-11-2017 %U http://ieeexplore.ieee.org/document/8004445/http://xplorestaging.ieee.org/ielx7/18/8071168/08004445.pdf?arnumber=8004445 %! IEEE Trans. Inform. Theory %R 10.1109/TIT.2017.2737546 %0 Journal Article %J JOURNAL OF MATHEMATICAL PHYSICS %D 2017 %T Genuine-multipartite entanglement criteria based on positive maps %A Clivaz, Fabien %A Huber, Marcus %A Lami, Ludovico %A Murta, Glaucia %X Positive maps applied to a subsystem of a bipartite quantum state constitute a central tool in characterising entanglement. In the multipartite case, however, the direct application of a positive but not completely positive map cannot distinguish if a state is genuinely multipartite entangled or just entangled across some bipartition. We thus generalise this bipartite concept to the multipartite setting by introducing non-positive maps that are positive on the subset of biseparable states but can map to a non-positive element if applied to a genuine multipartite entangled state. We explicitly construct examples of multipartite non-positive maps, obtained from positive maps via a lifting procedure, that in this fashion can reveal genuine multipartite entanglement in a robust way. Published by AIP Publishing. %B JOURNAL OF MATHEMATICAL PHYSICS %V 58 %8 aug %R 10.1063/1.4998433 %0 Journal Article %J PHYSICAL REVIEW LETTERS %D 2017 %T No-Go Theorem for the Characterization of Work Fluctuations in Coherent Quantum Systems %A Perarnau-Llobet, Marti %A Baumer, Elisa %A Hovhannisyan, Karen V. %A Huber, Marcus %A Acín, Antonio %XAn open question of fundamental importance in thermodynamics is howto describe the fluctuations of work for quantum coherent processes. In the standard approach, based on a projective energy measurement both at the beginning and at the end of the process, the first measurement destroys any initial coherence in the energy basis. Here we seek extensions of this approach which can possibly account for initially coherent states. We consider all measurement schemes to estimate work and require that (i) the difference of average energy corresponds to average work for closed quantum systems and that (ii) the work statistics agree with the standard two-measurement scheme for states with no coherence in the energy basis. We first show that such a scheme cannot exist. Next, we consider the possibility of performing collective measurements on several copies of the state and prove that it is still impossible to simultaneously satisfy requirements (i) and (ii). Nevertheless, improvements do appear, and in particular, we develop a measurement scheme that acts simultaneously on two copies of the state and allows us to describe a whole class of coherent transformations.

%B PHYSICAL REVIEW LETTERS %V 118 %R 10.1103/PhysRevLett.118.070601 %0 Journal Article %J Quantum %D 2017 %T Quantifying high dimensional entanglement with two mutually unbiased bases %A Erker, Paul %A Krenn, Mario %A Huber, Marcus %X Paul Erker, Mario Krenn, and Marcus Huber, Quantum 1, 22 (2017). https://doi.org/10.22331/q-2017-07-28-22 We derive a framework for quantifying entanglement in multipartite and high dimensional systems using only correlations in two unbiased bases. We furthermore develop such bounds in cases whe… %B Quantum %V 1 %P 22 %U https://quantum-journal.org/papers/q-2017-07-28-22/ %R 10.22331/q-2017-07-28-22 %0 Journal Article %J JOURNAL OF MATHEMATICAL PHYSICS %D 2017 %T Unitary 2-designs from random X- and Z-diagonal unitaries %A Nakata, Yoshifumi %A Hirche, Christoph %A Morgan, Ciara %A Winter, Andreas %XUnitary 2-designs are random unitaries simulating up to the second order statistical moments of the uniformly distributed random unitaries, often referred to as Haar random unitaries. They are used in a wide variety of theoretical and practical quantum information protocols and also have been used to model the dynamics in complex quantum many-body systems. Here, we show that unitary 2-designs can be approximately implemented by alternately repeating random unitaries diagonal in the Pauli-Z basis and Pauli-X basis. We also provide a converse about the number of repetitions needed to achieve unitary 2-designs. These results imply that the process after l repetitions achieves a Theta(d(-l))-approximate unitary 2-design. Based on the construction, we further provide quantum circuits that efficiently implement approximate unitary 2-designs. Although a more efficient implementation of unitary 2-designs is known, our quantum circuit has its own merit that it is divided into a constant number of commuting parts, which enables us to apply all commuting gates simultaneously and leads to a possible reduction of an actual execution time. We finally interpret the result in terms of the dynamics generated by time-dependent Hamiltonians and provide for the first time a random disordered time-dependent Hamiltonian that generates a unitary 2-design after switching interactions only a few times. Published by AIP Publishing.

%B JOURNAL OF MATHEMATICAL PHYSICS %V 58 %R 10.1063/1.4983266 %0 Journal Article %J Physical Review B %D 2016 %T Autonomous {Quantum} {Refrigerator} in a {Circuit}-{QED} {Architecture} {Based} on a {Josephson} {Junction} %A Hofer, Patrick P. %A Perarnau-Llobet, Marti %A Brask, Jonatan Bohr %A Silva, Ralph %A Huber, Marcus %A Brunner, Nicolas %K Condensed Matter - Mesoscale and Nanoscale Physics %K Quantum Physics %X An implementation of a small quantum absorption refrigerator in a circuit QED architecture is proposed. The setup consists of three harmonic oscillators coupled to a Josephson unction. The refrigerator is autonomous in the sense that it does not require any external control for cooling, but only thermal contact between the oscillators and heat baths at different temperatures. In addition, the setup features a built-in switch, which allows the cooling to be turned on and off. If timing control is available, this enables the possibility for coherence-enhanced cooling. Finally, we show that significant cooling can be achieved with experimentally realistic parameters and that our setup should be within reach of current technology. %B Physical Review B %V 94 %U http://arxiv.org/abs/1607.05218 %R 10.1103/PhysRevB.94.235420 %0 Journal Article %J Journal of Mathematical Physics %D 2016 %T Bipartite depolarizing maps %A Lami, Ludovico %A Huber, Marcus %X We introduce a 3-parameter class of maps (1) acting on a bipartite system which are a natural generalisation of the depolarizing channel (and include it as a special case). Then, we find the exact regions of the parameter space that alternatively determine a positive, completely positive, entanglement-breaking, or entanglement-annihilating map. This model displays a much richer behaviour than the one shown by a simple depolarizing channel, yet it stays exactly solvable. As an example of this richness, positive partial transposition but not entanglement-breaking maps is found in Theorem 2. A simple example of a positive yet indecomposable map is provided (see the Remark at the end of Section IV). The study of the entanglement-annihilating property is fully addressed by Theorem 7. Finally, we apply our results to solve the problem of the entanglement annihilation caused in a bipartite system by a tensor product of local depolarizing channels. In this context, a conjecture posed in the work of Filippov [J. Russ. Laser Res. 35, 484 (2014)] is affirmatively answered, and the gaps that the imperfect bounds of Filippov and Ziman [Phys. Rev. A 88, 032316 (2013)] left open are closed. To arrive at this result, we furthermore show how the Hadamard product between quantum states can be implemented via local operations. %B Journal of Mathematical Physics %V 57 %P 092201 %U http://aip.scitation.org/doi/10.1063/1.4962339 %R 10.1063/1.4962339 %0 Journal Article %J Physical Review A %D 2016 %T Heisenberg-{Weyl} {Observables}: {Bloch} vectors in phase space %A Asadian, Ali %A Erker, Paul %A Huber, Marcus %A Klockl, Claude %X We introduce a Hermitian generalization of Pauli matrices to higher dimensions which is based on Heisenberg-Weyl operators. The complete set of Heisenberg-Weyl observables allows us to identify a real-valued Bloch vector for an arbitrary density operator in discrete phase space, with a smooth transition to infinite dimensions. Furthermore, we derive bounds on the sum of expectation values of any set of anticommuting observables. Such bounds can be used in entanglement detection and we show that Heisenberg-Weyl observables provide a first nontrivial example beyond the dichotomic case. %B Physical Review A %V 94 %P 010301 %8 jul %U https://link.aps.org/doi/10.1103/PhysRevA.94.010301 %R 10.1103/PhysRevA.94.010301 %0 Journal Article %J Nature Communications %D 2016 %T Microcanonical and resource-theoretic derivations of the thermal state of a quantum system with noncommuting charges %A Yunger Halpern, Nicole %A Faist, Philippe %A Oppenheim, Jonathan %A Winter, Andreas %B Nature Communications %V 77 %P 12051 %8 Jul-07-2016 %U http://www.nature.com/doifinder/10.1038/ncomms12051 %! Nat Comms %R 10.1038/ncomms12051 %0 Journal Article %J Nature Photonics %D 2016 %T Multi-photon entanglement in high dimensions %A Malik, Mehul %A Erhard, Manuel %A Huber, Marcus %A Krenn, Mario %A Robert Fickler %A Anton Zeilinger %B Nature Photonics %I Nature Publishing Group %V 10 %P 248 - 252 %8 04/2016 %@ 1749-4885 %G eng %U http://dx.doi.org/10.1038/nphoton.2016.12 %N 4 %0 Journal Article %J IEEE Transactions on Information Theory %D 2016 %T Polar Codes in Network Quantum Information Theory %A Christoph Hirche %A Ciara Morgan %A Wilde, Mark M. %B IEEE Transactions on Information Theory %V 62 %P 915 - 924 %8 02/2016 %N 2 %! IEEE Trans. Inform. Theory %R 10.1109/TIT.2016.2514319 %0 Journal Article %J IEEE Transactions on Information Theory %D 2016 %T The Private and Public Correlation Cost of Three Random Variables With Collaboration %A Eric Chitambar %A Hsieh, Min-Hsiu %A Winter, Andreas %B IEEE Transactions on Information Theory %V 62 %P 2034-2043 %8 4/2016 %N 4 %! IEEE Trans. Inform. Theory %R 10.1109/TIT.2016.2530086 %0 Journal Article %J Physical Review Letters %D 2016 %T Quantifying {Entanglement} of {Maximal} {Dimension} in {Bipartite} {Mixed} {States} %A Sentís, Gael %A Eltschka, Christopher %A Gühne, Otfried %A Huber, Marcus %A Siewert, Jens %X The Schmidt coefficients capture all entanglement properties of a pure bipartite state and therefore determine its usefulness for quantum information processing. While the quantification of the corresponding properties in mixed states is important both from a theoretical and a practical point of view, it is considerably more difficult, and methods beyond estimates for the concurrence are elusive. In particular this holds for a quantitative assessment of the most valuable resource, the forms of entanglement that can only exist in high-dimensional systems. We derive a framework for lower bounding the appropriate measure of entanglement, the so-called G-concurrence, through few local measurements. Moreover, we show that these bounds have relevant applications also for multipartite states. %B Physical Review Letters %V 117 %P 190502 %U https://link.aps.org/doi/10.1103/PhysRevLett.117.190502 %R 10.1103/PhysRevLett.117.190502 %0 Journal Article %J Quantum Science and Technology %D 2016 %T Realising a quantum absorption refrigerator with an atom-cavity system %A Mitchison, Mark T. %A Huber, Marcus %A Prior, Javier %A Woods, Mischa P. %A Plenio, Martin B. %X An autonomous quantum thermal machine comprising a trapped atom or ion placed inside an optical cavity is proposed and analysed. Such a machine can operate as a heat engine whose working medium is the quantised atomic motion or as an absorption refrigerator that cools without any work input. Focusing on the refrigerator mode, we predict that it is possible with state-of-the-art technology to cool a trapped ion almost to its motional ground state using a thermal light source such as sunlight. We nonetheless find that a laser or a similar reference system is necessary to stabilise the cavity frequencies. Furthermore, we establish a direct and heretofore unacknowledged connection between the abstract theory of quantum absorption refrigerators and practical sideband cooling techniques. We also highlight and clarify some assumptions underlying several recent theoretical studies on self-contained quantum engines and refrigerators. Our work indicates that cavity quantum electrodynamics is a promising and versatile experimental platform for the study of autonomous thermal machines in the quantum domain. %B Quantum Science and Technology %V 1 %P 015001 %U http://stacks.iop.org/2058-9565/1/i=1/a=015001 %R 10.1088/2058-9565/1/1/015001 %0 Journal Article %J Phys. Rev. Lett. %D 2016 %T Relations between Coherence and Path Information %A E. Bagan %A Bergou, János A. %A Cottrell, Seth S. %A Hillery, Mark %B Phys. Rev. Lett. %I American Physical Society %V 116 %P 160406 %8 Apr %G eng %U http://link.aps.org/doi/10.1103/PhysRevLett.116.160406 %R 10.1103/PhysRevLett.116.160406 %0 Journal Article %J Journal of Physics A: Mathematical and Theoretical %D 2016 %T The role of quantum information in thermodynamics—a topical review %A Goold, John %A Huber, Marcus %A Riera, Arnau %A Rio, Lídia del %A Paul Skrzypczyk %B Journal of Physics A: Mathematical and Theoretical %V 49 %P 143001 %G eng %U http://stacks.iop.org/1751-8121/49/i=14/a=143001?key=crossref.ce80cac2171964cc6d6c51ed12d1e014 %R 10.1088/1751-8113/49/14/143001 %0 Journal Article %J Physical Review Letters %D 2016 %T Schur Complement Inequalities for Covariance Matrices and Monogamy of Quantum Correlations %A Lami, Ludovico %A Hirche, Christoph %A Adesso, Gerardo %A Winter, Andreas %B Physical Review Letters %V 117 %8 Jan-11-2016 %U http://link.aps.org/doi/10.1103/PhysRevLett.117.220502http://harvest.aps.org/v2/journals/articles/10.1103/PhysRevLett.117.220502/fulltexthttp://link.aps.org/article/10.1103/PhysRevLett.117.220502 %! Phys. Rev. Lett. %R 10.1103/PhysRevLett.117.220502 %0 Journal Article %J Physical Review Letters %D 2016 %T Should Entanglement Measures be Monogamous or Faithful? %A Lancien, Cécilia %A Di Martino, Sara %A Huber, Marcus %A Piani, Marco %A Adesso, Gerardo %A Winter, Andreas %B Physical Review Letters %V 117 %8 8/2016 %N 6 %! Phys. Rev. Lett. %R 10.1103/PhysRevLett.117.060501 %0 Journal Article %J Physical Review Letters %D 2016 %T Steering Maps and Their Application to Dimension-Bounded Steering %A Moroder, Tobias %A Gittsovich, Oleg %A Huber, Marcus %A Uola, Roope %A Gühne, Otfried %B Physical Review Letters %V 116 %G eng %U http://link.aps.org/doi/10.1103/PhysRevLett.116.090403 %R 10.1103/PhysRevLett.116.090403 %0 Journal Article %J New Journal of Physics %D 2016 %T Witnessing entanglement by proxy %A Bäuml, Stefan %A Bruß, Dagmar %A Huber, Marcus %A Kampermann, Hermann %A Winter, Andreas %B New Journal of Physics %V 18 %P 015002 %8 01/2016 %N 1 %! New J. Phys. %R 10.1088/1367-2630/18/1/015002 %0 Journal Article %J New Journal of Physics %D 2015 %T Autonomous quantum thermal machine for generating steady-state entanglement %A Bohr Brask, Jonatan %A Haack, Géraldine %A Nicolas Brunner %A Huber, Marcus %B New Journal of Physics %V 17 %P 113029 %8 nov %G eng %U http://stacks.iop.org/1367-2630/17/i=11/a=113029?key=crossref.0c6a75cb628f113c6cbd2a7b0d092f0d %R 10.1088/1367-2630/17/11/113029 %0 Journal Article %J Physical Review A %D 2015 %T Characterizing multipartite entanglement without shared reference frames %A Klöckl, C. %A Huber, M %B Physical Review A %V 91 %8 apr %G eng %U http://link.aps.org/doi/10.1103/PhysRevA.91.042339 %R 10.1103/PhysRevA.91.042339 %0 Journal Article %J New Journal of Physics %D 2015 %T Coherence-assisted single-shot cooling by quantum absorption refrigerators %A Mitchison, Mark T %A Woods, Mischa P %A Prior, Javier %A Huber, Marcus %B New Journal of Physics %V 17 %P 115013 %G eng %U http://stacks.iop.org/1367-2630/17/i=11/a=115013?key=crossref.3c2d7f1bc5de4bbea1cba38fd2236293 %R 10.1088/1367-2630/17/11/115013 %0 Web Page %D 2015 %T Decoupling with random diagonal-unitary matrices %A Yoshifumi Nakata %A Christoph Hirche %A Ciara Morgan %A Winter, Andreas %U http://arxiv.org/abs/1509.05155 %0 Journal Article %J Optica %D 2015 %T Experimental access to higher-dimensional entangled quantum systems using integrated optics %A Christoph Schaeff %A Robert Polster %A Huber, Marcus %A Ramelow, Sven %A Anton Zeilinger %K Integrated optics %K quantum optics %X Integrated optics allows for the generation and control of increasingly complex photonic states on chip-based architectures. Here, we implement two entangled qutrits&\#x2014;a nine-dimensional quantum system&\#x2014;and demonstrate an exceptionally high degree of experimental control. The approach, which is conceptually different to common bulk optical implementations, is heavily based on methods of integrated in-fiber and on-chip technologies and further motivated by methods commonly used in today&\#x2019;s telecommunications industry. The system is composed of an in-fiber source creating entangled qutrit states of any amplitude and phase, and an on-chip integrated general Multiport enabling the realization of any desired local unitary transformation within the two qutrit nine-dimensional Hilbert space. The complete design is readily extendible toward higher dimensions with moderate increase in complexity. Ultimately, our scheme allows for complete on-chip integration. We demonstrate the flexibility and generality of our system by realizing a complete characterization of the two-qutrit space of higher-order Einstein&\#x2013;Podolsky&\#x2013;Rosen correlations. %B Optica %I OSA %V 2 %P 523–529 %8 Jun %G eng %U http://www.osapublishing.org/optica/abstract.cfm?URI=optica-2-6-523 %R 10.1364/OPTICA.2.000523 %0 Journal Article %J Physical Review X %D 2015 %T Extractable Work from Correlations %A Martí Perarnau-Llobet %A Karen V. Hovhannisyan %A Huber, Marcus %A Paul Skrzypczyk %A Nicolas Brunner %A Acín, Antonio %B Physical Review X %V 5 %8 oct %G eng %U http://link.aps.org/doi/10.1103/PhysRevX.5.041011 %R 10.1103/PhysRevX.5.041011 %0 Web Page %D 2015 %T Implementing unitary 2-designs using random diagonal-unitary matrices %A Yoshifumi Nakata %A Christoph Hirche %A Ciara Morgan %A Winter, Andreas %U http://arxiv.org/abs/1502.07514 %0 Journal Article %J Nature Communications %D 2015 %T Limitations on quantum key repeaters %A Bäuml, Stefan %A Christandl, Matthias %A Horodecki, Karol %A Winter, Andreas %B Nature Communications %V 6 %P 6908 %8 4/2015 %! Nat Comms %R 10.1038/ncomms7908 %0 Journal Article %J Physical Review E %D 2015 %T Most energetic passive states %A Martí Perarnau-Llobet %A Karen V. Hovhannisyan %A Huber, Marcus %A Paul Skrzypczyk %A Tura, Jordi %A Acín, Antonio %B Physical Review E %V 92 %G eng %U http://link.aps.org/doi/10.1103/PhysRevE.92.042147 %R 10.1103/PhysRevE.92.042147 %0 Journal Article %J Journal of Physics A: Mathematical and Theoretical %D 2015 %T Relaxations of separability in multipartite systems: Semidefinite programs, witnesses and volumes %A Lancien, Cécilia %A Gühne, Otfried %A Sengupta, Ritabrata %A Huber, Marcus %B Journal of Physics A: Mathematical and Theoretical %V 48 %P 505302 %G eng %U http://stacks.iop.org/1751-8121/48/i=50/a=505302?key=crossref.2e93a28de5494676a0b866fa95ccebfd %R 10.1088/1751-8113/48/50/505302 %0 Journal Article %J New Journal of Physics %D 2015 %T Thermodynamic cost of creating correlations %A Huber, Marcus %A Martí Perarnau-Llobet %A Karen V. Hovhannisyan %A Paul Skrzypczyk %A Klöckl, Claude %A Nicolas Brunner %A Acín, Antonio %B New Journal of Physics %V 17 %P 065008 %G eng %U http://stacks.iop.org/1367-2630/17/i=6/a=065008?key=crossref.b9c20f4bb628b09efcb912347c01851e %R 10.1088/1367-2630/17/6/065008 %0 Journal Article %J Physical Review E %D 2015 %T Thermodynamics of creating correlations: {Limitations} and optimal protocols %A Bruschi, David Edward %A Martí Perarnau-Llobet %A Friis, Nicolai %A Karen V. Hovhannisyan %A Huber, Marcus %B Physical Review E %V 91 %8 mar %G eng %U http://link.aps.org/doi/10.1103/PhysRevE.91.032118 %R 10.1103/PhysRevE.91.032118 %0 Journal Article %J Physical Review E %D 2014 %T Entanglement enhances cooling in microscopic quantum refrigerators %A Nicolas Brunner %A Huber, Marcus %A Noah Linden %A Sandu Popescu %A Ralph Silva %A Paul Skrzypczyk %X Small self-contained quantum thermal machines function without external source of work or control, but using only incoherent interactions with thermal baths. Here we investigate the role of entanglement in a small self-contained quantum refrigerator. We first show that entanglement is detrimental as far as efficiency is concerned---fridges operating at efficiencies close to the Carnot limit do not feature any entanglement. Moving away from the Carnot regime, we show that entanglement can enhance cooling and energy transport. Hence a truly quantum refrigerator can outperform a classical one. Furthermore, the amount of entanglement alone quantifies the enhancement in cooling. %B Physical Review E %V 89 %8 3/2014 %N 3 %! Phys. Rev. E %R 10.1103/PhysRevE.89.032115 %0 Journal Article %J Journal of Physics A: Mathematical and Theoretical %D 2014 %T Fifty years of Bell’s theorem %A Nicolas Brunner %A Gühne, Otfried %A Huber, Marcus %B Journal of Physics A: Mathematical and Theoretical %V 47 %P 420301 %8 oct %G eng %U http://stacks.iop.org/1751-8121/47/i=42/a=420301?key=crossref.9d548f14fc7338685392dcd6228de98d %R 10.1088/1751-8113/47/42/420301 %0 Journal Article %J Proceedings of the National Academy of Sciences %D 2014 %T Generation and confirmation of a (100 x 100)-dimensional entangled quantum system %A Krenn, M. %A Huber, M %A Fickler, R. %A Lapkiewicz, R. %A Ramelow, S. %A Zeilinger, A. %X Entangled quantum systems have properties that have fundamentally overthrown the classical worldview. Increasing the complexity of entangled states by expanding their dimensionality allows the implementation of novel fundamental tests of nature, and moreover also enables genuinely new protocols for quantum information processing. Here we present the creation of a (100x100)-dimensional entangled quantum system, using spatial modes of photons. For its verification we develop a novel nonlinear criterion which infers entanglement dimensionality of a global state by using only information about its subspace correlations. This allows very practical experimental implementation as well as highly efficient extraction of entanglement dimensionality information. Applications in quantum cryptography and other protocols are very promising. %B Proceedings of the National Academy of Sciences %V 111 %P 6243 - 6247 %8 04/2014 %N 17 %! Proceedings of the National Academy of Sciences %R 10.1073/pnas.1402365111 %0 Journal Article %J Linear Algebra and its Applications %D 2014 %T Inequalities for the ranks of multipartite quantum states %A Josh Cadney %A Huber, Marcus %A Noah Linden %A Winter, Andreas %X We investigate relations between the ranks of marginals of multipartite quantum states. These are the Schmidt ranks across all possible bipartitions and constitute a natural quantification of multipartite entanglement dimensionality. We show that there exist inequalities constraining the possible distribution of ranks. This is analogous to the case of von Neumann entropy (\alpha-R\'enyi entropy for \alpha=1), where nontrivial inequalities constraining the distribution of entropies (such as e.g. strong subadditivity) are known. It was also recently discovered that all other \alpha-R\'enyi entropies for α∈(0,1)∪(1,∞) satisfy only one trivial linear inequality (non-negativity) and the distribution of entropies for α∈(0,1) is completely unconstrained beyond non-negativity. Our result resolves an important open question by showing that also the case of \alpha=0 (logarithm of the rank) is restricted by nontrivial linear relations and thus the cases of von Neumann entropy (i.e., \alpha=1) and 0-R\'enyi entropy are exceptionally interesting measures of entanglement in the multipartite setting. %B Linear Algebra and its Applications %V 452 %P 153 - 171 %8 07/2014 %! Linear Algebra and its Applications %R 10.1016/j.laa.2014.03.035 %0 Journal Article %J Nature Communications %D 2014 %T Interface between path and orbital angular momentum entanglement for high-dimensional photonic quantum information %A Robert Fickler %A Radek Lapkiewicz %A Huber, Marcus %A Lavery, Martin P.J. %A Padgett, Miles J. %A Anton Zeilinger %X Photonics has become a mature field of quantum information science, where integrated optical circuits offer a way to scale the complexity of the setup as well as the dimensionality of the quantum state. On photonic chips, paths are the natural way to encode information. To distribute those high-dimensional quantum states over large distances, transverse spatial modes, like orbital angular momentum (OAM) possessing Laguerre Gauss modes, are favourable as flying information carriers. Here we demonstrate a quantum interface between these two vibrant photonic fields. We create three-dimensional path entanglement between two photons in a non-linear crystal and use a mode sorter as the quantum interface to transfer the entanglement to the OAM degree of freedom. Thus our results show a novel, flexible way to create high-dimensional spatial mode entanglement. Moreover, they pave the way to implement broad complex quantum networks where high-dimensionally entangled states could be distributed over distant photonic chips. %B Nature Communications %V 5 %8 7/2014 %! Nat Comms %R 10.1038/ncomms5502 %0 Journal Article %J IEEE Transactions on Information Theory %D 2014 %T The Quantum Reverse Shannon Theorem and Resource Tradeoffs for Simulating Quantum Channels %A Bennett, Charles H. %A Devetak, Igor %A Harrow, Aram W. %A Shor, Peter W. %A Winter, Andreas %B IEEE Transactions on Information Theory %V 60 %P 2926-2959 %8 5/2014 %N 5 %! IEEE Trans. Inform. Theory %R 10.1109/TIT.2014.2309968 %0 Journal Article %J Physical Review Letters %D 2014 %T Steering Bound Entangled States: A Counterexample to the Stronger Peres Conjecture %A Moroder, Tobias %A Gittsovich, Oleg %A Huber, Marcus %A Gühne, Otfried %X Quantum correlations are at the heart of many applications in quantum information science and, at the same time, they form the basis for discussions about genuine quantum effects and their difference to classical physics. On one hand, entanglement theory provides the tools to quantify correlations in information processing and many results have been obtained to discriminate useful entanglement, which can be distilled to a pure form, from bound entanglement, being of limited use in many applications. On the other hand, for discriminating quantum phenomena from their classical counterparts, Schr\"odinger and Bell introduced the notions of steering and local hidden variable models. We provide a method to generate systematically bound entangled quantum states which can still be used for steering and therefore to rule out local hidden state models. This sheds light on the relations between the various views on quantum correlations and disproves a widespread conjecture known as the stronger Peres conjecture. For practical applications, it implies that even the weakest form of entanglement can be certified in a semi-device independent way. %B Physical Review Letters %V 113 %8 8/2014 %N 5 %! Phys. Rev. Lett. %R 10.1103/PhysRevLett.113.050404 %0 Conference Proceedings %B 9th Conference on the Theory of Quantum Computation, Communication and Cryptography (TQC 2014) %D 2014 %T Strong Converse for the Quantum Capacity of the Erasure Channel for Almost All Codes %A Wilde, Mark M. %A Winter, Andreas %E Steve T Flammia %E Harrow, Aram W. %B 9th Conference on the Theory of Quantum Computation, Communication and Cryptography (TQC 2014) %I LIPICS %C Singapore %V 27 %P 52-66 %R 10.4230/LIPIcs.TQC.2014.52 %0 Journal Article %J Physical Review A %D 2014 %T Unified approach to entanglement criteria using the Cauchy-Schwarz and Hölder inequalities %A Wölk, Sabine %A Huber, Marcus %A Gühne, Otfried %X We present a unified approach to different recent entanglement criteria. Although they were developed in different ways, we show that they are all applications of a more general principle given by the Cauchy-Schwarz inequality. We explain this general principle and show how to use it to derive not only already known entanglement criteria, but also criteria which were unknown so far. We systematically investigate its potential and limitations to detect bipartite and multipartite entanglement. Furthermore, we describe how to apply our generalized entanglement detection scheme to find the measurement directions to verify the entanglement of a given state experimentally. %B Physical Review A %V 90 %8 8/2014 %N 2 %! Phys. Rev. A %R 10.1103/PhysRevA.90.022315 %0 Journal Article %J Physical Review Letters %D 2014 %T Witnessing Genuine Multipartite Entanglement with Positive Maps %A Huber, Marcus %A Sengupta, Ritabrata %X We derive a general framework that connects every positive map with a corresponding witness for partial separability in multipartite quantum systems. We show that many previous approaches were intimately connected to the witnesses derived from partial transposition and that such criteria can easily be outperformed in higher dimensions by non-decomposable maps. As an exemplary case we present a witness that is capable of detecting genuine multipartite entanglement in bound entangled states. %B Physical Review Letters %V 113 %8 9/2014 %N 10 %! Phys. Rev. Lett. %R 10.1103/PhysRevLett.113.100501 %0 Journal Article %J Physical Review Letters %D 2013 %T Bose-Glass Phases of Ultracold Atoms due to Cavity Backaction %A Hessam Habibian %A André Winter %A Paganelli, Simone %A Heiko Rieger %A Giovanna Morigi %X We determine the quantum ground-state properties of ultracold bosonic atoms interacting with the mode of a high-finesse resonator. The atoms are confined by an external optical lattice, whose period is incommensurate with the cavity mode wavelength, and are driven by a transverse laser, which is resonant with the cavity mode. While for pointlike atoms photon scattering into the cavity is suppressed, for sufficiently strong lasers quantum fluctuations can support the buildup of an intracavity field, which in turn amplifies quantum fluctuations. The dynamics is described by a Bose-Hubbard model where the coefficients due to the cavity field depend on the atomic density at all lattice sites. Quantum Monte Carlo simulations and mean-field calculations show that, for large parameter regions, cavity backaction forces the atoms into clusters with a checkerboard density distribution. Here, the ground state lacks superfluidity and possesses finite compressibility, typical of a Bose glass. This system constitutes a novel setting where quantum fluctuations give rise to effects usually associated with disorder. %B Physical Review Letters %V 110 %8 2/2013 %U http://prl.aps.org/abstract/PRL/v110/i7/e075304 %N 7 %! Phys. Rev. Lett. %R 10.1103/PhysRevLett.110.075304 %0 Journal Article %J Physical Review A %D 2013 %T Entangled singularity patterns of photons in {Ince}-{Gauss} modes %A Krenn, Mario %A Robert Fickler %A Huber, Marcus %A Radek Lapkiewicz %A Plick, William %A Ramelow, Sven %A Anton Zeilinger %B Physical Review A %V 87 %8 jan %G eng %U http://link.aps.org/doi/10.1103/PhysRevA.87.012326 %R 10.1103/PhysRevA.87.012326 %0 Journal Article %J Physical Review Letters %D 2013 %T Entanglement Generation is Not Necessary for Optimal Work Extraction %A Hovhannisyan, Karen %A Martí Perarnau-Llobet %A Huber, Marcus %A Acín, Antonio %X We consider reversible work extraction from identical quantum batteries. From an ensemble of individually passive states, work can be produced only via global unitary (and thus entangling) operations. However, we show here that there always exists a method to extract all possible work without creating any entanglement, at the price of generically requiring more operations (i.e. additional time). We then study faster methods to extract work and provide a quantitative relation between the amount of generated multipartite entanglement and extractable work. Our results suggest a general relation between entanglement generation and the power of work extraction. %B Physical Review Letters %V 111 %8 12/2013 %N 24 %! Phys. Rev. Lett. %R 10.1103/PhysRevLett.111.240401 %0 Journal Article %J Physical Review A %D 2013 %T Entropy vector formalism and the structure of multidimensional entanglement in multipartite systems %A Huber, Marcus %A Martí Perarnau-Llobet %A de Vicente, Julio I. %B Physical Review A %V 88 %8 10/2013 %U http://arxiv.org/abs/1307.3541 %N 4 %! Phys. Rev. A %R 10.1103/PhysRevA.88.042328 %0 Journal Article %J Quantum Information Processing %D 2013 %T Examining the dimensionality of genuine multipartite entanglement %A Spengler, Christoph %A Huber, Marcus %A Gabriel, Andreas %A Hiesmayr, Beatrix C. %B Quantum Information Processing %V 12 %P 269–278 %G eng %U http://link.springer.com/10.1007/s11128-012-0369-8 %R 10.1007/s11128-012-0369-8 %0 Journal Article %J New Journal of Physics %D 2013 %T Proving the generation of genuine multipartite entanglement in a single-neutron interferometer experiment %A Erdösi, Daniel %A Huber, Marcus %A Hiesmayr, Beatrix C. %A Hasegawa, Yuji %B New Journal of Physics %V 15 %P 023033 %G eng %U http://stacks.iop.org/1367-2630/15/i=2/a=023033?key=crossref.b714f63bb49eb9e64ce9a70aa4a6ddfe %R 10.1088/1367-2630/15/2/023033 %0 Journal Article %J New Journal of Physics %D 2013 %T Quantum hypergraph states %A Rossi, M %A Huber, M %A Bruß, D. %A Macchiavello, C. %B New Journal of Physics %V 15 %P 113022 %8 11/2013 %N 11 %! New J. Phys. %R 10.1088/1367-2630/15/11/113022 %0 Journal Article %J Phyiscal Review A %D 2013 %T Quantum phases of incommensurate optical lattices due to cavity backaction %A Hessam Habibian %A André Winter %A Paganelli, Simone %A Heiko Rieger %A Giovanna Morigi %B Phyiscal Review A %V 88 %P 043618 %0 Journal Article %J IEEE Transactions on Information Theory %D 2013 %T Quantum Rate-Distortion Coding With Auxiliary Resources %A Wilde, Mark M. %A Datta, Nilanjana %A Hsieh, Min-Hsiu %A Winter, Andreas %B IEEE Transactions on Information Theory %V 59 %P 6755 - 6773 %8 10/2013 %N 10 %! IEEE Trans. Inform. Theory %R 10.1109/TIT.2013.2271772 %0 Journal Article %J Journal of Mathematical Physics %D 2013 %T Quantum-to-classical rate distortion coding %A Datta, Nilanjana %A Hsieh, Min-Hsiu %A Wilde, Mark M. %A Winter, Andreas %B Journal of Mathematical Physics %V 54 %P 042201 %8 2013 %N 4 %! J. Math. Phys. %R 10.1063/1.4798396 %0 Journal Article %J Physical Review Letters %D 2013 %T Structure of Multidimensional Entanglement in Multipartite Systems %A Huber, Marcus %A de Vicente, Julio I. %X We explore the structure of multipartite quantum systems which are entangled in multiple degrees of freedom. We find necessary and sufficient conditions for the characterization of tripartite systems and necessary conditions for any number of parties. Furthermore we develop a framework of multilevel witnesses for efficient discrimination and quantification of multidimensional entanglement that is applicable for an arbitrary number of systems and dimensions. %B Physical Review Letters %V 110 %8 1/2013 %N 3 %! Phys. Rev. Lett. %R 10.1103/PhysRevLett.110.030501 %0 Journal Article %J Physical Review A %D 2013 %T Weak randomness in device-independent quantum key distribution and the advantage of using high-dimensional entanglement %A Huber, Marcus %A Pawłowski, Marcin %B Physical Review A %V 88 %8 9/2013 %N 3 %! Phys. Rev. A %R 10.1103/PhysRevA.88.032309 %0 Journal Article %J Phys. Rev. Lett. %D 2011 %T All Nonclassical Correlations Can Be Activated into Distillable Entanglement %A Piani, Marco %A Gharibian, Sevag %A Adesso, Gerardo %A Calsamiglia, John %A Horodecki, Paweł %A Winter, Andreas %B Phys. Rev. Lett. %I American Physical Society %V 106 %P 220403 %8 Jun %U http://prl.aps.org/abstract/PRL/v106/i22/e220403 %) http://arxiv.org/abs/1103.4032 %R 10.1103/PhysRevLett.106.220403 %0 Journal Article %J Phys. Rev. Lett. %D 2011 %T Bell Inequalities with No Quantum Violation and Unextendable Product Bases %A Remigiusz Augusiak %A Julia Stasińska %A Hadley, Christopher %A Korbicz, Jarosław K. %A Lewenstein, Maciej %A Acín, Antonio %X The strength of classical correlations is subject to certain constraints, commonly known as Bell inequalities. Violation of these inequalities is the manifestation of nonlocality—displayed, in particular, by quantum mechanics, meaning that quantum mechanics can outperform classical physics at tasks associated with such Bell inequalities. Interestingly, however, there exist situations in which this is not the case. We associate an intriguing class of bound entangled states, constructed from unextendable product bases with a wide family of tasks, for which (i) quantum correlations do not outperform the classical ones but (ii) there exist supraquantum nonsignaling correlations that do provide an advantage. %B Phys. Rev. Lett. %I American Physical Society %V 107 %P 070401 %8 Aug %R 10.1103/PhysRevLett.107.070401 %0 Journal Article %J International Journal of Quantum Information %D 2011 %T Characterizing quantumness via entanglement creation %A Gharibian, Sevag %A Piani, Marco %A Adesso, Gerardo %A Calsamiglia, John %A Pawel Horodecki %B International Journal of Quantum Information %V 9 %P 1701-1713 %8 05 %U http://arxiv.org/abs/1105.3419 %R 10.1142/S0219749911008258 %0 Journal Article %J Physical Review A %D 2011 %T Quantifying, characterizing, and controlling information flow in ultracold atomic gases %A Haikka, P. %A McEndoo, S. %A De Chiara, G. %A G. M. Palma %A Maniscalco, S. %X We study quantum information flow in a model comprised of a trapped impurity qubit immersed in a Bose-Einstein-condensed reservoir. We demonstrate how information flux between the qubit and the condensate can be manipulated by engineering the ultracold reservoir within experimentally realistic limits. We show that this system undergoes a transition from Markovian to non-Markovian dynamics, which can be controlled by changing key parameters such as the condensate scattering length. In this way, one can realize a quantum simulator of both Markovian and non-Markovian open quantum systems, the latter ones being characterized by a reverse flow of information from the background gas (reservoir) to the impurity (system). %B Physical Review A %V 84 %8 9/2011 %U http://pra.aps.org/abstract/PRA/v84/i3/e031602 %N 3 %! Phys. Rev. A %R 10.1103/PhysRevA.84.031602 %0 Conference Paper %B AIP Conference Proceedings %D 2007 %T Kaonic Quantitative Complementarity and Quantum Erasers %A Bramon, Albert %A Garbarino, G. %A Hiesmayr, B. C. %B AIP Conference Proceedings %V 962 %P 242 %G eng %U http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=APCPCS000962000001000242000001&idtype=cvips&gifs=yes %0 Journal Article %J Acta Physica Polonica B %D 2007 %T Quantum Mechanics with Neutral Kaons %A Bramon, Albert %A Garbarino, G. %A Hiesmayr, B. C. %B Acta Physica Polonica B %V 38 %P 2763–2776 %G eng %U http://arxiv.org/abs/hep-ph/0703152 %0 Journal Article %J Journal of Physics B: Atomic, Molecular and Optical Physics %D 2007 %T Weighted graph states and applications to spin chains, lattices and gases %A Hartmann, L. %A Calsamiglia, John %A Dür, Wolfgang %A Briegel, Hans J. %B Journal of Physics B: Atomic, Molecular and Optical Physics %V 40 %P S1 %G eng %U http://www.iop.org/EJ/abstract/0953-4075/40/9/S01 %R 10.1088/0953-4075/40/9/S01 %0 Journal Article %J arXiv %D 2006 %T Kaonic Quantum Erasers at KLOE 2: "Erasing the Present, changing the Past'' %A Bramon, Albert %A Garbarino, G. %A Hiesmayr, B. H %K Quantum Physics %X Neutral kaons are unique quantum systems to show some of the most puzzling peculiarities of quantum mechanics. Here we focus on a quantitative version of Bohr's complementary principle and on quantum marking and eraser concepts. In detail we show that neutral kaons (1) are kind of double slit devices encapsulating Bohr's complementarity principle in a simple and transparent way, and (2) offer marking and eraser options which are not afforded by other quantum systems and which can be performed at the DAPHNE machine. %B arXiv %8 11/2006 %G eng %U http://www.arxiv.org/pdf/hep-ph/0609314.pdf http://arxiv.org/abs/hep-ph/0609314 %0 Journal Article %J Foundations of Physics %D 2006 %T Unitarity as Preservation of Entropy and Entanglement in Quantum Systems %A Hulpke, Florian %A Poulsen, Uffe %A Sanpera, Anna %A Sen(De), Aditi %A Sen, Ujjwal %A Lewenstein, Maciej %X Abstract The logical structure of Quantum Mechanics (QM) and its relation to other fundamental principles of Nature has been for decades a subject of intensive research. In particular, the question whether the dynamical axiom of QM can be derived from other principles has been often considered. In this contribution, we show that unitary evolutions arise as a consequences of demanding preservation of entropy in the evolution of a single pure quantum system, and preservation of entanglement in the evolution of composite quantum systems. 6 %B Foundations of Physics %V 36 %P 477–499 %8 04/2006 %G eng %U http://www.springerlink.com/content/tjg6r668u462848r/fulltext.pdf %R 10.1007/s10701-005-9035-7 %0 Conference Paper %B Laser Spectroscopy: Proceedings of the XVII International Conference, Aviemore, Scotland UK, 19-24 June 2005 %D 2005 %T Disordered complex systems using cold gases and trapped ions %A Sen(De), Aditi %A Sen, Ujjwal %A Lewenstein, Maciej %A Ahufinger, Veronica %A Pons, Marisa %A Sanpera, Anna %E Hinds, E. A. %E Ferguson, A. %E Riis, E. %B Laser Spectroscopy: Proceedings of the XVII International Conference, Aviemore, Scotland UK, 19-24 June 2005 %I World Scientific %C Singapore %P 158–166 %G eng %U http://arxiv.org/abs/quant-ph/0508018 %0 Journal Article %J Physical Review Letters %D 2005 %T Spin Gases: Quantum Entanglement Driven by Classical Kinematics %A Calsamiglia, John %A Hartmann, L. %A Dür, Wolfgang %A Briegel, Hans J. %K entanglement distribution %K spin gas %X A spin gas is a natural extension of a classical gas. It consists of a large number of particles whose (random) motion is described classically, but, in addition, have internal (quantum mechanical) degrees of freedom that interact during collisions. For specific types of quantum interactions we determine the entanglement that occurs naturally in such systems. We analyze how the evolution of the quantum state is determined by the underlying classical kinematics of the gas. For the Boltzmann gas, we calculate the rate at which entanglement is produced and characterize the entanglement properties of the equilibrium state. %B Physical Review Letters %V 95 %P 180502 %8 10/2005 %G eng %U http://link.aps.org/abstract/PRL/v95/e180502 %R 10.1103/PhysRevLett.95.180502 %0 Journal Article %J Physical Review A %D 2004 %T Active and passive quantum erasers for neutral kaons %A Bramon, A. %A Garbarino, G. %A Hiesmayr, B. %B Physical Review A %V 69 %G eng %U http://pra.aps.org/abstract/PRA/v69/i6/e062111 %R 10.1103/PhysRevA.69.062111 %0 Journal Article %J Physical Review Letters %D 2004 %T Experimental Detection of Multipartite Entanglement using Witness Operators %A Bourennane, Mohamed %A Eibl, Manfred %A Kurtsiefer, Christian %A Gaertner, Sascha %A Weinfurter, Harald %A Gühne, Otfried %A Hyllus, Philipp %A Bruß, Dagmar %A Lewenstein, Maciej %A Sanpera, Anna %B Physical Review Letters %V 92 %G eng %U http://prl.aps.org/abstract/PRL/v92/i8/e087902 %R 10.1103/PhysRevLett.92.087902 %0 Book Section %B Symmetries in Gravity and Field Theory %D 2004 %T Passive Quantum Erasure for Neutral Kaons %A Bramon, Albert %A Garbarino, G. %A Hiesmayr, B. C. %E Aldaya, V. %E Cervero, J. M. %B Symmetries in Gravity and Field Theory %I Ediciones Universidad de Salamanca %C Salamanca %P 223 %G eng %U http://arxiv.org/abs/quant-ph/0404086 %0 Journal Article %J Physical Review A %D 2004 %T Quantitative complementarity in two-path interferometry %A Bramon, A. %A Garbarino, G. %A Hiesmayr, B. %B Physical Review A %V 69 %G eng %U http://pra.aps.org/abstract/PRA/v69/i2/e022112 %R 10.1103/PhysRevA.69.022112 %0 Journal Article %J Physical Review Letters %D 2004 %T Quantum Marking and Quantum Erasure for Neutral Kaons %A Bramon, A. %A Garbarino, G. %A Hiesmayr, B. %B Physical Review Letters %V 92 %G eng %U http://prl.aps.org/abstract/PRL/v92/i2/e020405 %R 10.1103/PhysRevLett.92.020405 %0 Journal Article %J Quantum Information and Computation %D 2004 %T Simplifying Schmidt number witnesses via higher-dimensional embeddings %A Hulpke, F. %A Bruss, Dagmar %A Lewenstein, Maciej %A Sanpera, Anna %B Quantum Information and Computation %V 4 %P 207 %G eng %0 Journal Article %J Physics Letters A %D 2004 %T Violation of a Bell inequality in particle physics experimentally verified? %A Bertlmann, R. A. %A Bramon, Albert %A Garbarino, G. %A Hiesmayr, B. C. %K Bell inequality %K Entanglement %X Relevant aspects for testing Bell inequalities with entangled meson–antimeson systems are analyzed. In particular, we argue that the results of Go [J. Mod. Opt. 51 (2004) 991], which nicely illustrate the quantum entanglement of B-meson pairs, cannot be considered as a Bell-test refuting local realism. %B Physics Letters A %V 332 %P 355–360 %G eng %U http://www.sciencedirect.com/science?\_ob=ArticleURL&\_udi=B6TVM-4DK6240-1&\_user=1517286&\_coverDate=11%2F22%2F2004&\_rdoc=1&\_fmt=high&\_orig=search&\_sort=d&\_docanchor=&view=c&\_searchStrId=1201715030&\_rerunOrigin=google&\_acct=C000053449&\_version=1 %R 10.1016/j.physleta.2004.10.006 %0 Book Section %B Quantum Information Processing %D 2003 %T Entanglement properties of composite quantum systems %A Eckert, Kai %A Guhne, O. %A Hulpke, Florian %A Hyllus, Philipp %A Korbicz, J. %A Mompart, Jordi %A Bruss, Dagmar %A Lewenstein, Maciej %A Sanpera, Anna %E Leuchs, G. %E Beth, T. %B Quantum Information Processing %I Wilew-VCH %C Berlin %P 87–95 %@ 352740371X %G eng %0 Journal Article %J Journal of Modern Optics %D 2003 %T Experimental detection of entanglement via witness operators and local measurements %A Gühne, Otfried %A Hyllus, Philipp %A Bruss, Dagmar %A Ekert, Artur K. %A Lewenstein, Maciej %A Macchiavello, Chiara %A Sanpera, Anna %B Journal of Modern Optics %V 50 %P 1079–1102 %G eng %U http://www.informaworld.com/smpp/36433790-99697256/content\~{}db=all\~{}content=a713826204 %R 10.1080/09500340308234554 %0 Journal Article %J The European Physical Journal C - Particles and Fields %D 2003 %T Quantitative duality and neutral kaon interferometry %A Bramon, A. %A Garbarino, Gianni %A Hiesmayr, B. C. %X A quantitative formulation of Bohr&\#8217;s complementarity principle and interferometric duality is discussed and applied to the neutral kaon system. Recent measurements by the CPLEAR Collaboration can be easily interpreted in terms of neutral kaon interferometry, illustrating and confirming those basic principles of quantum mechanics. The subject can be further investigated at the operational \$\backslash phi\$ -factory Daphne. %B The European Physical Journal C - Particles and Fields %V 32 %P 377–380 %8 01/2003 %G eng %U http://www.springerlink.com/content/4l12acw6kn9xkfbt %R 10.1140/epjc/s2003-01444-5 %0 Conference Paper %B eConf C0309101:THWP005 %D 2003 %T Quantitative duality and quantum erasure for neutral kaons %A Bramon, Albert %A Garbarino, Gianni %A Hiesmayr, Beatrix C. %B eConf C0309101:THWP005 %G eng %0 Journal Article %J Physical Review A %D 2002 %T Detection of entanglement with few local measurements %A Gühne, O. %A Hyllus, P. %A Bruß, D. %A Ekert, A. %A Lewenstein, M. %A Macchiavello, C. %A Sanpera, A. %B Physical Review A %V 66 %G eng %U http://pra.aps.org/abstract/PRA/v66/i6/e062305 %R 10.1103/PhysRevA.66.062305