Quantum thermometry by single-qubit dephasing

Razavian, Sholeh; Benedetti, Claudia; Bina, Matteo; Akbari-Kourbolagh, Y.; Paris, Matteo G. A.

doi:10.1140/epjp/i2019-12708-9

Cited by 62 publications

(54 citation statements)

References 54 publications

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“…However, if time is not considered a resource, we found that the best estimate is obtained upon using two qubits in a product states, each one subject to a local environment, i.e. the best strategy is to repeat twice a single-qubit probe measurement [17,18]. Notice that the notions of same bath or two independent replicas of the same bath do not require multiple physical systems to be implemented in practice.…”

Section: Discussionmentioning

confidence: 94%

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Two-qubit quantum probes for the temperature of an Ohmic environment

et al. 2020

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We address a particular instance where open quantum systems may be used as quantum probes for an emergent property of a complex system, as the temperature of a thermal bath. The inherent fragility of the quantum probes against decoherence is the key feature making the overall scheme very sensitive. The specific setting examined here is that of quantum thermometry, which aims to exploits decoherence as resource to estimate the temperature of a sample. We focus on temperature estimation for a bosonic bath at equilibrium in the Ohmic regime (ranging from sub-Ohmic to super-Ohmic), by using pairs of qubits in different initial states and interacting with different environments, consisting either of a single thermal bath, or of two independent ones at the same temperature. Our scheme involves pure dephasing of the probes, thus avoiding energy exchange with the sample and the consequent perturbation of temperature itself. We discuss the interplay between correlations among the probes and correlations within the bath, and show that entanglement improves thermometry at short times whereas, if the interaction time is not constrained, coherence rather than entanglement, is the key resource in quantum thermometry.

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Section: Discussionmentioning

confidence: 94%

“…On the contrary, if we can wait for longer times, the (absolute) best strategy is sending sequentially two qubits prepared in a |+ state through the bath, i.e. repeating twice the single-qubit scheme [18]. In Fig.…”

Section: B Separable Qubitsmentioning

confidence: 99%

Two-qubit quantum probes for the temperature of an Ohmic environment

et al. 2020

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“…We note that POVMs provide the most general measurements in quantum theory [32]. They include scenarios where auxiliary systems interact in an arbitrary way with the system of interest as well as measurements that exploit quantum coherence [6,9,10,[33][34][35][36][37][38][39]. Each of the POVM elements corresponds to an outcome m which will be observed with probability…”

Section: Framework For Temperature Measurementsmentioning

confidence: 99%

Fundamental limits on low-temperature quantum thermometry with finite resolution

Potts

Brask

Brunner

2019

Quantum

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While the ability to measure low temperatures accurately in quantum systems is important in a wide range of experiments, the possibilities and the fundamental limits of quantum thermometry are not yet fully understood theoretically. Here we develop a general approach to low-temperature quantum thermometry, taking into account restrictions arising not only from the sample but also from the measurement process. We derive a fundamental bound on the minimal uncertainty for any temperature measurement that has a finite resolution. A similar bound can be obtained from the third law of thermodynamics. Moreover, we identify a mechanism enabling sub-exponential scaling, even in the regime of finite resolution. We illustrate this effect in the case of thermometry on a fermionic tightbinding chain with access to only two lattice sites, where we find a quadratic divergence of the uncertainty. We also give illustrative examples of ideal quantum gases and a squarelattice Ising model, highlighting the role of phase transitions.

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“…In the latter part of this paper, we explicitly calculate this upper bound for two examples: single-qubit states and two-qubit X-states. These states appear in many applications of quantum information theory [4,29,[36][37][38][39]. This paper is organised as follows.…”

Section: Introductionmentioning

confidence: 99%

An upper bound on the number of compatible parameters in simultaneous quantum estimation

Kukita¹

2020

J. Phys. A: Math. Theor.

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Simultaneous estimation of multiple parameters is required in many practical applications. A lower bound on the variance of simultaneous estimation is given by the quantum Fisher information matrix. This lower bound is, however, not necessarily achievable. There exists a necessary and sufficient condition for its achievability. It is unknown how many parameters can be estimated while satisfying this condition. In this paper, we analyse an upper bound on the number of such parameters through linear-algebraic techniques. This upper bound depends on the algebraic structure of the quantum system used as a probe. We explicitly calculate this bound for two quantum systems: single qubit and two-qubit X-states.

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Quantum thermometry by single-qubit dephasing

Cited by 62 publications

References 54 publications

Two-qubit quantum probes for the temperature of an Ohmic environment

Two-qubit quantum probes for the temperature of an Ohmic environment

Fundamental limits on low-temperature quantum thermometry with finite resolution

An upper bound on the number of compatible parameters in simultaneous quantum estimation

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