Orthogonality Catastrophe as a Consequence of the Quantum Speed Limit

Fogarty, Thomás; Deffner, Sebastian; Busch, Thomas; Campbell, Steve

doi:10.1103/physrevlett.124.110601

Cited by 86 publications

(53 citation statements)

References 74 publications

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“…The exact results for the nonadiabatic energy fluctuations we have provided are expected to have widespread applications in both theoretical and experimental studies of these systems. For example, they can be used to characterize far-from-equilibrium dynamics in ultracold gases, quantify the cost of quantum control such as the use of optimal protocols [ 68 , 76 , 77 , 78 ] and shortcuts to adiabaticity [ 41 , 42 ], characterize the performance of devices and processes in quantum thermodynamics [ 30 ], and study the ultimate speed limits [ 37 , 38 ], quantum decay [ 35 ] and orthogonality catastrophe [ 79 ] under scale-invariant quantum dynamics.…”

Section: Conclusion and Discussionmentioning

confidence: 99%

Nonadiabatic Energy Fluctuations of Scale-Invariant Quantum Systems in a Time-Dependent Trap

Beau

Campo

2020

Entropy

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We consider the nonadiabatic energy fluctuations of a many-body system in a time-dependent harmonic trap. In the presence of scale-invariance, the dynamics becomes self-similar and the nondiabatic energy fluctuations can be found in terms of the initial expectation values of the second moments of the Hamiltonian, square position, and squeezing operators. Nonadiabatic features are expressed in terms of the scaling factor governing the size of the atomic cloud, which can be extracted from time-of-flight images. We apply this exact relation to a number of examples: the single-particle harmonic oscillator, the one-dimensional Calogero-Sutherland model, describing bosons with inverse-square interactions that includes the non-interacting Bose gas and the Tonks-Girdardeau gas as limiting cases, and the unitary Fermi gas. We illustrate these results for various expansion protocols involving sudden quenches of the trap frequency, linear ramps and shortcuts to adiabaticity. Our results pave the way to the experimental study of nonadiabatic energy fluctuations in driven quantum fluids.

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Section: Conclusion and Discussionmentioning

confidence: 99%

Nonadiabatic Energy Fluctuations of Scale-Invariant Quantum Systems in a Time-Dependent Trap

Beau

Campo

2020

Entropy

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“…We focus on a promising setup that has already been realized in the laboratory [53][54][55], where the gas atoms effectively interact only with the impurities and not with each other. In this setting, the Anderson orthogonality catastrophe (OC) [56,57] imprints characteristic signatures on the decoherence dynamics of the impurity [58][59][60][61], which can be observed using Ramsey interferometry [54,62,63]. The optimal precision of our thermometry protocol can be evaluated in terms of the quantum Fisher information, and we reveal a tradeoff between measurement time and precision controlled by the impurity-gas interaction strength.…”

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confidence: 94%

In Situ Thermometry of a Cold Fermi Gas via Dephasing Impurities

et al. 2020

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The precise measurement of low temperatures is a challenging, important, and fundamental task for quantum science. In particular, in situ thermometry is highly desirable for cold atomic systems due to their potential for quantum simulation. Here, we demonstrate that the temperature of a noninteracting Fermi gas can be accurately inferred from the nonequilibrium dynamics of impurities immersed within it, using an interferometric protocol and established experimental methods. Adopting tools from the theory of quantum parameter estimation, we show that our proposed scheme achieves optimal precision in the relevant temperature regime for degenerate Fermi gases in current experiments. We also discover an intriguing trade-off between measurement time and thermometric precision that is controlled by the impurity-gas coupling, with weak coupling leading to the greatest sensitivities. This is explained as a consequence of the slow decoherence associated with the onset of the Anderson orthogonality catastrophe, which dominates the gas dynamics following its local interaction with the immersed impurity.

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“…As the size grows, the maximum fidelity with no dynamical decoupling decreases with the system size. A possible explanation to this drop in fidelities for growing system sizes can be found in the orthogonality catastrophe arising from the quantum speed limit as recently studied by Fogarty et al in Reference [ 36 ]. However, for the FAQUAD protocols studied we observe that the fidelity can (sometimes significantly) be increased thanks to dynamical decoupling.…”

Section: Uniform All-to-all Interactionsmentioning

confidence: 99%

Towards Generation of Cat States in Trapped Ions Set-Ups via FAQUAD Protocols and Dynamical Decoupling

Palmero

Simón

Poletti

2019

Entropy

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The high fidelity generation of strongly entangled states of many particles, such as cat states, is a particularly demanding challenge. One approach is to drive the system, within a certain final time, as adiabatically as possible, in order to avoid the generation of unwanted excitations. However, excitations can be generated also by the presence of dissipative effects such as dephasing. Here we compare the effectiveness of Local Adiabatic and the FAst QUasi ADiabatic protocols in achieving a high fidelity for a target superposition state both with and without dephasing. In particular we consider trapped ions set-ups in which each spin interacts with all the others with the uniform coupling strength or with a power-law coupling. In order to mitigate the effects of dephasing, we complement the adiabatic protocols with dynamical decoupling and we test its effectiveness. The protocols we study could be readily implemented with state-of-the-art techniques.

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Orthogonality Catastrophe as a Consequence of the Quantum Speed Limit

Cited by 86 publications

References 74 publications

Nonadiabatic Energy Fluctuations of Scale-Invariant Quantum Systems in a Time-Dependent Trap

Nonadiabatic Energy Fluctuations of Scale-Invariant Quantum Systems in a Time-Dependent Trap

In Situ Thermometry of a Cold Fermi Gas via Dephasing Impurities

Towards Generation of Cat States in Trapped Ions Set-Ups via FAQUAD Protocols and Dynamical Decoupling

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