Using Polarons for sub-nK Quantum Nondemolition Thermometry in a Bose-Einstein Condensate

Mehboudi, Mohammad; Lampo, Aniello; Charalambous, Christos; Correa, Luis Alfonso; García-March, Miguel Ángel; Lewenstein, Maciej

doi:10.1103/physrevlett.122.030403

Cited by 102 publications

(89 citation statements)

References 56 publications

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“…a two-level system, may interact with a sample system in a thermal state, and subsequently be measured to estimate the temperature. If the probe reaches thermal equilibrium with the sample, or a nonequilibrium steady state, optimal designs of the probe and of the probesystem interaction can be determined [13][14][15][16][17][18]. Outside of the steady state regime, it was found that access to the transient probe dynamics may outperform the steady-state protocols [19][20][21], that dynamical control acts as a resource [22][23][24], and that thermometry can in some cases be mapped to a phase estimation problem [25,26].…”

Section: Introductionmentioning

confidence: 99%

Tight bound on finite-resolution quantum thermometry at low temperatures

Jørgensen

Potts

Paris

et al. 2020

Phys. Rev. Research

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Precise thermometry is of wide importance in science and technology in general and in quantum systems in particular. Here, we investigate fundamental precision limits for thermometry on cold quantum systems, taking into account constraints due to finite measurement resolution. We derive a tight bound on the optimal precision scaling with temperature, as the temperature approaches zero. The bound demonstrates that under finite resolution, the variance in any temperature estimate must decrease slower than linearly. This scaling can be saturated by monitoring the nonequilibrium dynamics of a single-qubit probe. We support this finding by numerical simulations of a spin-boson model. In particular, this shows that thermometry with a vanishing absolute error at low temperature is possible with finite resolution, answering an interesting question left open by previous work. Our results are relevant both fundamentally, as they illuminate the ultimate limits to quantum thermometry, and practically, in guiding the development of sensitive thermometric techniques applicable at ultracold temperatures.

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Section: Introductionmentioning

confidence: 99%

Tight bound on finite-resolution quantum thermometry at low temperatures

Jørgensen

Potts

Paris

et al. 2020

Phys. Rev. Research

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“…Under certain regularity assumptions, the QFI matrix encodes the ultimate precision bounds on the estimation of unknown parameters encoded in a density matrix (know as quantum Cramer-Rao bounds), while the SLDs and their commutators determine whether such bounds may be saturated with physically realizable measurements [5,6]. The associated applications are plenty, including phase and frequency estimation [4,[7][8][9][10][11][12][13][14][15][16][17], estimation of noise parameters [18][19][20][21][22][23], joint estimation of unitary and/or noisy parameters [24][25][26][27][28][29][30][31], sub-wavelength resolution of optical sources [32][33][34][35][36][37][38], nano-scale thermometry [39][40][41][42][43][44][45], and estimation of Hamiltonian parameters in the presence of phase-transitions [46][47][48]. The most common approach for ...…”

Section: Introductionmentioning

confidence: 99%

Non-orthogonal bases for quantum metrology

Genoni¹,

Tufarelli²

2019

J. Phys. A: Math. Theor.

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Many quantum statistical models are most conveniently formulated in terms of non-orthonormal bases. This is the case, for example, when mixtures and superpositions of coherent states are involved. In these instances, we show that the analytical evaluation of the quantum Fisher information may be greatly simplified by bypassing both the diagonalization of the density matrix and the orthogonalization of the basis. The key ingredient in our method is the Gramian matrix (i.e. the matrix of scalar products between basis elements), which may be interpreted as a metric tensor for index contraction. As an application, we derive novel analytical results for several estimation problems involving noisy Schrödinger cat states.

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“…Moreover, reducing the bath size will allow following the transition from a Markov to a non-Markov bath, shedding new light on the microscopic quantum dynamics for system-bath entanglement [34]. Finally, our experimental system also paves the way to local probing of quantum gases or employing collective interaction effects [35].…”

mentioning

confidence: 99%

Single-Atom Quantum Probes for Ultracold Gases Boosted by Nonequilibrium Spin Dynamics

et al. 2020

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Quantum probes are atomic-sized devices mapping information of their environment to quantum mechanical states. By improving measurements and at the same time minimizing perturbation of the environment, they form a central asset for quantum technologies. We realize spin-based quantum probes by immersing individual Cs atoms into an ultracold Rb bath. Controlling inelastic spin-exchange processes between probe and bath allows mapping motional and thermal information onto quantum-spin states. We show that the steady-state spin-population is well suited for absolute thermometry, reducing temperature measurements to detection of quantum spin distributions. Moreover, we find that the information gain per inelastic collision can be maximized by accessing the nonequilibrium spin dynamic. The sensitivity of nonequilibrium quantum probing effectively beats the steady-state Cramér Rao limit of quantum probing by almost an order of magnitude, while reducing the perturbation of the bath to only three quanta of angular momentum. Our work paves the way for local probing of quantum systems at the Heisenberg limit, and moreover for optimizing measurement strategies via control of nonequilibrium dynamics.

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Using Polarons for sub-nK Quantum Nondemolition Thermometry in a Bose-Einstein Condensate

Cited by 102 publications

References 56 publications

Tight bound on finite-resolution quantum thermometry at low temperatures

Tight bound on finite-resolution quantum thermometry at low temperatures

Non-orthogonal bases for quantum metrology

Single-Atom Quantum Probes for Ultracold Gases Boosted by Nonequilibrium Spin Dynamics

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