Qubit thermometry for micromechanical resonators

Brunelli, Matteo; Olivares, Stefano; Paris, Matteo G. A.

doi:10.1103/physreva.84.032105

Cited by 110 publications

(128 citation statements)

References 49 publications

(55 reference statements)

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“…It was shown in [16] that the principles of interferometric quantum-enhanced metrology can be applied to the measurement of temperature, allowing one at least in principle to achieve HL scaling. In several other systems the sensitivity of quantum mechanical interference to thermal noise was already used for thermometry [29,30], but no attempts were made for establishing the ultimate sensitivity of such an approach.…”

mentioning

confidence: 99%

Precision measurements of temperature and chemical potential of quantum gases

Marzolino¹,

Braun²

2013

Phys. Rev. A

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We investigate the sensitivity with which the temperature and the chemical potential characterizing quantum gases can be measured. We calculate the corresponding quantum Fisher information matrices for both fermionic and bosonic gases. For the latter, particular attention is devoted to the situation close to the Bose-Einstein condensation transition, which we examine not only for the standard scenario in three dimensions, but also for generalized condensation in lower dimensions, where the bosons condense in a subspace of Hilbert space instead of a unique ground state, as well as condensation at fixed volume or fixed pressure. We show that Bose Einstein condensation can lead to sub-shot noise sensitivity for the measurement of the chemical potential. We also examine the influence of interactions on the sensitivity in three different models, and show that mean-field and contact interactions deteriorate the sensitivity but only slightly for experimentally accessible weak interactions.

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mentioning

confidence: 99%

Precision measurements of temperature and chemical potential of quantum gases

Marzolino¹,

Braun²

2013

Phys. Rev. A

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“…The qubit-oscillator coupling shown in Eq. (16) (and its limit under rotating-wave approximation) has already been addressed concerning the estimation of the temperature of a mechanical resonator in thermal equilibrium, and the optimality of energy measurements performed on the qubit to this purpose has been shown [38,39]. This motivates the choice of that specific form of interaction, given that according to Eq.…”

Section: Hybrid Optomechanics For Discrete-variable Probingmentioning

confidence: 99%

Quantum-limited estimation of continuous spontaneous localization

et al. 2017

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We apply the formalism of quantum estimation theory to extract information about potential collapse mechanisms of the continuous spontaneous localisation (CSL) form. In order to estimate the strength with which the field responsible for the CSL mechanism couples to massive systems, we consider the optomechanical interaction between a mechanical resonator and a cavity field. Our estimation strategy passes through the probing of either the state of the oscillator or that of the electromagnetic field that drives its motion. In particular, we concentrate on all-optical measurements, such as homodyne and heterodyne measurements. We also compare the performances of such strategies with those of a spin-assisted optomechanical system, where the estimation of the CSL parameter is performed through time-gated spin-like measurements.Understanding the nature of the quantum-to-classical (QtC) transition is a long-sought problem that attracts an evergrowing attention [1][2][3][4][5][6]. While quantum mechanics has undergone exhaustive and extremely successful testings in the microscopic realm, the apparent absence of quantum manifestations at the macroscopic scale cries for a deeper understanding. In particular, this lack of evidence reinforces the need of assessing the causes for the emergence of classical mechanics from fundamental quantum evolution. The most widely accepted theory behind such process is quantum decoherence [6]: The environment surrounding any quantum system monitors its state continuously, practically collapsing the system's wavefunction and curtailing any quantum behaviour. Such process is conjectured to occur more quickly with the growing size of the system at hand. Under this regime, macroscopic superpositions would be possible in macroscopic systems perfectly isolated from their environment, a condition that is, for all practical purposes, not realisable.However, a set of theories, usually referred to as collapse models (CMs), suggests an alternative route to the explanation of the QtC transition by putting forward fundamental underlying mechanisms responsible for the collapse of the wavefunction [7]. The strength of this effect should increase with the size (mass) of the system, leaving microscopic (macroscopic) systems fully within the quantum (classical) realm. The key difference between CMs and standard quantum mechanics is that in the framework entailed by the former, perfectly isolated macroscopic objects would continue to act classically.Among the proposals put forward so far to test (or rule out) some of the currently formulated CMs [8][9][10], those based on the experimental platform of cavity optomechanics offer features of undemanding scalability of the mass of the system to be probed and high-sensitivity of measurement. Most remarkably, at variance with standardly pursued approaches [11], they bypass the need for the construction and quantum-limited management of large interferometers [12,13]. notwithstanding such promising features, the investigation of CMs still poses considerable experim...

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“…In fact, quantum estimation theory has been successfully employed for the estimation of static noise parameters [43,44,45,46,47] and in several other scenarios, as for example quantum thermometry [48].…”

Section: The Physical Modelmentioning

confidence: 99%

Quantum probes for fractional Gaussian processes

Paris¹

2014

Physica A: Statistical Mechanics and its Applications

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We address the characterization of classical fractional random noise via quantum probes. In particular, we focus on estimation and discrimination problems involving the fractal dimension of the trajectories of a system subject to fractional Brownian noise. We assume that the classical degree of freedom exposed to the environmental noise is coupled to a quantum degree of freedom of the same system, e.g. its spin, and exploit quantum limited measurements on the spin part to characterize the classical fractional noise. More generally, our approach may be applied to any two-level system subject to dephasing perturbations described by fractional Brownian noise, in order to assess the precision of quantum limited measurements in the characterization of the external noise. In order to assess the performances of quantum probes we evaluate the Bures metric, as well as the Helstrom and the Chernoff bound, and optimize their values over the interaction time. We find that quantum probes may be successfully employed to obtain a reliable characterization of fractional Gaussian process when the coupling with the environment is weak or strong. In the first case decoherence is not much detrimental and for long interaction times the probe acquires information about the environmental parameters without being too much mixed. Conversely, for strong coupling information is quickly impinged on the quantum probe and can effectively retrieved by measurements performed in the early stage of the evolution. In the intermediate situation, none of the two above effects take place: information is flowing from the environment to the probe too slowly compared to decoherence, and no measurements can be effectively employed to extract it from the quantum probe. The two regimes of weak and strong coupling are defined in terms of a threshold value of the coupling, which itself increases with the fractional dimension.

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Qubit thermometry for micromechanical resonators

Cited by 110 publications

References 49 publications

Precision measurements of temperature and chemical potential of quantum gases

Precision measurements of temperature and chemical potential of quantum gases

Quantum-limited estimation of continuous spontaneous localization

Quantum probes for fractional Gaussian processes

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