@article {friis_flexible_2017,
title = {Flexible resources for quantum metrology},
journal = {New Journal of Physics},
volume = {19},
number = {6},
year = {2017},
pages = {063044},
abstract = {Quantum metrology offers a quadratic advantage over classical approaches to parameter estimation problems by utilising entanglement and nonclassicality. However, the hurdle of actually implementing the necessary quantum probe states and measurements, which vary drastically for different metrological scenarios, is usually not taken into account. We show that for a wide range of tasks in metrology, 2D cluster states (a particular family of states useful for measurement-based quantum computation) can serve as flexible resources that allow one to efficiently prepare any required state for sensing, and perform appropriate (entangled) measurements using only single qubit operations. Crucially, the overhead in the number of qubits is less than quadratic, thus preserving the quantum scaling advantage. This is ensured by using a compression to a logarithmically sized space that contains all relevant information for sensing. We specifically demonstrate how our method can be used to obtain optimal scaling for phase and frequency estimation in local estimation problems, as well as for the Bayesian equivalents with Gaussian priors of varying widths. Furthermore, we show that in the paradigmatic case of local phase estimation 1D cluster states are sufficient for optimal state preparation and measurement.},
issn = {1367-2630},
doi = {10.1088/1367-2630/aa7144},
url = {http://stacks.iop.org/1367-2630/19/i=6/a=063044},
author = {Friis, Nicolai and Orsucci, Davide and Skotiniotis, Michalis and Sekatski, Pavel and Dunjko, Vedran and Briegel, Hans J. and D{\"u}r, Wolfgang}
}
@article {Hartmann2007,
title = {Weighted graph states and applications to spin chains, lattices and gases},
journal = {Journal of Physics B: Atomic, Molecular and Optical Physics},
volume = {40},
number = {9},
year = {2007},
pages = {S1},
doi = {10.1088/0953-4075/40/9/S01},
url = {http://www.iop.org/EJ/abstract/0953-4075/40/9/S01},
author = {Hartmann, L. and Calsamiglia, John and D{\"u}r, Wolfgang and Briegel, Hans J.}
}
@article {SenDe2006,
title = {Quantum-information processing in disordered and complex quantum systems},
journal = {Physical Review A (Atomic, Molecular, and Optical Physics)},
volume = {74},
number = {6},
year = {2006},
month = {12/2006},
pages = {062309{\textendash}8},
keywords = {information theory, quantum entanglement, quantum gates, radiation pressure},
doi = {10.1103/PhysRevA.74.062309},
url = {http://link.aps.org/abstract/PRA/v74/e062309},
author = {Sen(De), Aditi and Sen, Ujjwal and Ahufinger, Veronica and Briegel, Hans J. and Sanpera, Anna and Lewenstein, Maciej}
}
@article {Calsamiglia2005,
title = {Spin Gases: Quantum Entanglement Driven by Classical Kinematics},
journal = {Physical Review Letters},
volume = {95},
number = {18},
year = {2005},
month = {10/2005},
pages = {180502},
abstract = {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.},
keywords = {entanglement distribution, spin gas},
doi = {10.1103/PhysRevLett.95.180502},
url = {http://link.aps.org/abstract/PRL/v95/e180502},
author = {Calsamiglia, John and Hartmann, L. and D{\"u}r, Wolfgang and Briegel, Hans J.}
}