Quantum metrology out of equilibrium

Razavian, Sholeh; Paris, Matteo G. A.

doi:10.1016/j.physa.2019.03.125

Cited by 15 publications

(13 citation statements)

References 39 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%

“…The single-qubit case has already been described in previous works, dealing with the purely dephasing bath, related both to the estimation of temperature or other bath parameters [16][17][18][19]. Here we focus, under the same conditions, on the two-qubit probe scenario, which allows us to explore the role of quantum correlations and the number of qubits in inferring the temperature.…”

Section: Physical Modelmentioning

confidence: 99%

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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%

Section: Physical Modelmentioning

confidence: 99%

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

et al. 2020

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“…In this context, a relevant feature of our probing technique is the pure dephasing nature of the interaction between the qubit and its environment. This means that, while the ohmic system has a fixed temperature, the probe has access to the full set of out-of-equilibrium states [ 22 ], while not exchanging energy with the ohmic system. As we will see, this provides room to optimize the probing strategy and to enhance sensitivity over classical (thermal) probes.…”

Section: Introductionmentioning

confidence: 99%

Quantum Probes for Ohmic Environments at Thermal Equilibrium

Sehdaran

Bina²,

Benedetti³

et al. 2019

Entropy

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It is often the case that the environment of a quantum system may be described as a bath of oscillators with an ohmic density of states. In turn, the precise characterization of these classes of environments is a crucial tool to engineer decoherence or to tailor quantum information protocols. Recently, the use of quantum probes in characterizing ohmic environments at zero-temperature has been discussed, showing that a single qubit provides precise estimation of the cutoff frequency. On the other hand, thermal noise often spoil quantum probing schemes, and for this reason we here extend the analysis to a complex system at thermal equilibrium. In particular, we discuss the interplay between thermal fluctuations and time evolution in determining the precision attainable by quantum probes. Our results show that the presence of thermal fluctuations degrades the precision for low values of the cutoff frequency, i.e., values of the order ω c ≲ T (in natural units). For larger values of ω c , decoherence is mostly due to the structure of environment, rather than thermal fluctuations, such that quantum probing by a single qubit is still an effective estimation procedure.

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“…The topic has become of interest in the last two decades, due to the development of controlled quantum systems at the classical-quantum boundary [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20], which makes it relevant to have a precise determination of temperature for quantum systems [21][22][23][24][25][26][27] and to understand the ultimate bounds to precision in the estimation of temperature [28][29][30][31][32][33][34][35][36][37][38][39]. At the same time, precise manipulation of quantum systems makes it possible to design and realize quantum thermometers, i.e., thermometers where temperature is precisely estimated looking at tiny changes in genuine quantum features such as entanglement or coherence [40][41][42][43].…”

Section: Introductionmentioning

confidence: 99%

Role of topology in determining the precision of a finite thermometer

et al. 2021

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Temperature fluctuations of a finite system follow the Landau bound δT 2 = T 2 /C(T ) where C(T ) is the heat capacity of the system. In turn, the same bound sets a limit to the precision of temperature estimation when the system itself is used as a thermometer. In this paper, we employ graph theory and the concept of Fisher information to assess the role of topology on the thermometric performance of a given system. We find that low connectivity is a resource to build precise thermometers working at low temperatures, whereas highly connected systems are suitable for higher temperatures. Upon modeling the thermometer as a set of vertices for the quantum walk of an excitation, we compare the precision achievable by position measurement to the optimal one, which itself corresponds to energy measurement.

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Quantum metrology out of equilibrium

Cited by 15 publications

References 39 publications

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

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

Quantum Probes for Ohmic Environments at Thermal Equilibrium

Role of topology in determining the precision of a finite thermometer

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