Coherent and Dephasing Spectroscopy for Single-Impurity Probing of an Ultracold Bath

Adam, Daniel; Bouton, Quentin; Nettersheim, Jens; Burgardt, Sabrina; Widera, Artur

doi:10.1103/physrevlett.129.120404

Cited by 16 publications

(16 citation statements)

References 44 publications

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“…The experimentally relevant example of an impurity immersed in an ultracold Fermi gas [10] highlights the rich physics which is unveiled from considering the thermodynamics of decoherence. However, our framework can equally well be applied to a range of other situations, such as ultracold bosonic environments where dephasing impurities have recently been realized [13,23], as well as strongly interacting systems. We hope that our work will inspire further investigations of the peculiar thermodynamic features of decoherence and associated properties in diverse physical settings.…”

Section: Discussionmentioning

confidence: 99%

“…According to equation (2.2), the qubit coherence evolves as ρ^S10false(tfalse)=normale−iϵtνfalse(tfalse)ρ^S10false(0false), where νfalse(tfalse)=falsefalse⟨normaleiH^0t normale−iH^1tfalsefalse⟩B is the decoherence function with H^0=H^B and H^1=H^B+gc^1†c^1. This complex function may be experimentally extracted by applying a second π/2-pulse with a variable phase and measuring the final qubit populations [10,13,23].…”

Section: Qubit Decoherence In a Fermionic Lattice Environmentmentioning

confidence: 99%

“…the quantum measurement process and the emergence of classical reality [6,7]. Moreover, the dynamics of decoherence can now be studied in carefully controlled experiments [8][9][10][11][12][13] and harnessed for non-destructive measurements using auxiliary probes [14][15][16][17][18][19][20][21][22][23]. A better understanding of the decoherence process is thus important both for modern scientific applications and for the foundations of quantum physics.…”

Section: Introductionmentioning

confidence: 99%

“…Decoherence is not only a major limiting factor for entanglement-enhanced metrology [3] and scalable quantum computation [4,5], but is also fundamental for the quantum measurement process and the emergence of classical reality [6,7]. Moreover, the dynamics of decoherence can now be studied in carefully controlled experiments [8–13] and harnessed for non-destructive measurements using auxiliary probes [14–23]. A better understanding of the decoherence process is thus important both for modern scientific applications and for the foundations of quantum physics.…”

Section: Introductionmentioning

confidence: 99%

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Thermodynamics of decoherence

2023

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We investigate the non-equilibrium thermodynamics of pure decoherence. In a pure decoherence process, the system Hamiltonian is a constant of motion and there is no direct energy exchange between the system and its surroundings. Nevertheless, the environment’s energy is not generally conserved and in this work we show that this leads to non-trivial heat dissipation as a result of decoherence alone. This heat has some very distinctive properties: it obeys an integral fluctuation relation and can be interpreted in terms of the entropy production associated with populations in the energy eigenbasis of the initial state. We show that the heat distribution for a pure decoherence process is different from the distribution of work done by the initial system–bath interaction quench. Instead, it corresponds to a mixture of work distributions of cyclical processes, each conditioned on a state of the open system. Inspired by recent experiments on impurities in ultracold gases, we demonstrate our general results by studying the heat generated by the decoherence of a qubit immersed within a degenerate Fermi gas in the lowest band of a species-selective optical lattice.

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Section: Discussionmentioning

confidence: 99%

Section: Qubit Decoherence In a Fermionic Lattice Environmentmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Thermodynamics of decoherence

2023

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“…Also, in the σ =↓ sector this is the 0-th eigenstate with energy E ↓ 0 = 0. In experiments a typical protocol is Ramsey spectroscopy [18][19][20], which consists in starting with the noninteracting impurity and applying two π/2 pulses separated by a time t. Varying t allows to probe the response…”

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confidence: 99%

Two-dimensional polaron spectroscopy of Fermi superfluids

Amelio¹

2022

Preprint

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Multidimensional spectroscopy is becoming an increasingly popular tool and there is an ongoing effort to access electronic transitions and many-body dynamics in correlated materials. We apply the protocol recently proposed by Wang [1] to extract two-dimensional polaron spectra in a Fermi superfluid with an impurity. The bath is descibed by a BCS ansatz and it assumed that the impurity can scatter at most one quasiparticle pair. The spectral response contains a symmetric contribution, which carries the same information as Ramsey spectra, and an asymmetric one. While a priori it may seem promising to probe the quasiparticle gap from the asymmetric contribution, we show explicitly that this is not the case and, in the absence of incoherent processes, multidimensional spectroscopy does not bring much additional information. Our calculation is suitable for 3D ultracold gases, but we discuss implications for exciton-polarons in 2D materials.

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Measuring the environment of a Cs qubit with dynamical decoupling sequences

Burgardt¹,

Jäger²,

Julian³

et al. 2023

J. Phys. B: At. Mol. Opt. Phys.

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We report the experimental implementation of dynamical decoupling on a small, non-interacting ensemble of up to 25 optically trapped, neutral Cs atoms. The qubit consists of the two magnetic-insensitive Cs clock states |F = 3,mF = 0⟩ and |F = 4,mF = 0⟩, which are coupled by microwave radiation. We observe a significant enhancement of the coherence time when employing Carr-Purcell-Meiboom-Gill (CPMG) dynamical decoupling. A CPMG sequence with ten refocusing pulses increases the coherence time of 16.2(9) ms by more than one order of magnitude to 178(2) ms. In addition, we make use of the filter function formalism and utilize the CPMG sequence to measure the background noise floor affecting the qubit coherence, finding a power-law noise spectrum 1/ω^α with α = 0.89(2). This finding is in very good agreement with an independent measurement of the noise in the intensity of the trapping laser. Moreover, the measured coherence evolutions also exhibit signatures of low-frequency noise originating at distinct frequencies. Our findings point toward noise spectroscopy of engineered atomic baths through single-atom dynamical decoupling in a system of individual Cs impurities immersed in an ultracold 87Rb bath.

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Coherent and Dephasing Spectroscopy for Single-Impurity Probing of an Ultracold Bath

Cited by 16 publications

References 44 publications

Thermodynamics of decoherence

Thermodynamics of decoherence

Two-dimensional polaron spectroscopy of Fermi superfluids

Measuring the environment of a Cs qubit with dynamical decoupling sequences

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