Quantum-Heat Fluctuation Relations in Three-Level Systems Under Projective Measurements

Giachetti, Guido; Gherardini, Stefano; Trombettoni, Andrea; Ruffo, Stefano

doi:10.3390/condmat5010017

Cited by 12 publications

(13 citation statements)

References 49 publications

(70 reference statements)

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“…namely, as a consequence of the protocol applied on the qubit, the latter gets randomised into the completely mixed state ρ = 1/2. The phenomenon of randomisation induced by a train of measurements has been observed and discussed earlier, see e.g., [7,[20][21][22], but here it occurs as a consequence a different mecahnism. After preparation in a state that is diagonal in the σ z basis, the qubit undergoes a rotation of a vanishingly small angle in the large N limit.…”

Section: Robustness Of Fluctuation Theorems To Intermediate Projectiv...supporting

confidence: 50%

Experimental verification of fluctuation relations with a quantum computer

Solfanelli,

Santini,

Campisi

2021

Preprint

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Inspired by the idea that quantum computers can be useful in advancing basic science, we use a quantum processor to experimentally validate a number of theoretical results in non-equilibrium quantum thermodynamics, that were not (or were very little) corroborated so far. In order to do so, we first put forward a novel method to implement the so called two point measurement scheme, which is at the basis of the study of non-equilibrium energetic exchanges in quantum systems. Like the well-established interferometric method, our method uses an ancillary system, but at variance with it, it provides direct access to the energy exchange statistics, rather than its Fourier transform, thus being extremely more effective. We first experimentally validate our ancilla-assisted two point measurement scheme, and then apply it to i) experimentally verify that fluctuation theorems are robust against projective measurements, a theoretical prediction which was not validated so far, ii) experimentally verify the so called heat engine fluctuation relation, by implementing a SWAP quantum heat engine. iii) experimentally verify that the heat engine fluctuation relation continues to hold in presence of intermediate measurements, by implementing the design at the basis of the so called quantum-measurement-cooling concept. For both engines, we report the measured average heat and work exchanged and single out their operation mode. Our experiments constitute the experimental basis for the understanding of the non-equilibrium energetics of quantum computation and for the implementation of energy management devices on quantum processors.

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Section: Robustness Of Fluctuation Theorems To Intermediate Projectiv...supporting

confidence: 50%

Experimental verification of fluctuation relations with a quantum computer

Solfanelli,

Santini,

Campisi

2021

Preprint

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“…The study of sequence of quantum measurements, especially projective ones, is broad and covers several topics, ranging from fundamental quantum physics and quantum Zeno phenomena [8][9][10][11][12][13][14][15][16][17][18], quantum metrology and sensing [19][20][21][22][23][24] to quantum thermodynamics [25][26][27][28][29][30][31][32][33][34][35][36][37], both at the theoretical and experimental level. An active line of research focused on the characterization of the thermodynamics principles ruling the statistics of the measurement outcomes, with several contributions making use of quantum fluctuation theorems and Jarzynski relations [38][39][40][41][42][43][44].…”

Section: Introductionmentioning

confidence: 99%

“…Within this framework, since each measurement entails a sudden energy variation with a given probability, one can also analyze the probability distribution of the heat exchanged by a monitored quantum system with its surroundings, as done in Refs. [33,37] for two and three-level quantum systems.…”

Section: Introductionmentioning

confidence: 99%

Thermalization processes induced by quantum monitoring in multi-level systems

Gherardini,

Giachetti,

Ruffo

et al. 2020

Preprint

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We study the heat statistics of an N -dimensional quantum system monitored by a sequence of projective measurements. The late-time, asymptotic properties of the heat characteristic function are analyzed in the thermodynamic limit of a high, ideally infinite, number of measurements. In this context, conditions allowing for Infinite-Temperature Thermalization (ITT), induced by the monitoring of the quantum system, are discussed. We show that ITT is identified by the fixed point of a symmetric random matrix that models the stochastic process originated by the sequence of measurements. Such fixed point is independent on the non-equilibrium evolution of the system and its initial state. Exceptions to ITT take place when the observable of the intermediate measurements is commuting (or quasi-commuting) with the Hamiltonian of the system, or when the time interval between measurements is smaller or comparable with the energy scale of the quantum system (quantum Zeno regime). Results on the limit of infinite-dimensional Hilbert spaces (N → ∞) -describing continuous systems with a discrete spectrum -are presented. By denoting with M the number of quantum measurements, we show that the order of the limits M → ∞ and N → ∞ matters: when N is fixed and M diverges, then there is ITT. In the opposite case, the system becomes classical, so that the measurements are no longer effective in changing the state of the system. A non trivial result is obtained fixing M/N 2 where partial ITT occurs. Finally, an example of incomplete thermalization applicable to rotating two-dimensional gases is presented.

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“…For this purpose, each probability P j is decomposed in the product of two contributions: One is thermal and is associated to the inverse temperature β fin , while the other is a correction term that accounts for the (geometric) distance λ concerning ρ fin from being thermal [72]. Specifically, given the set {E j } of the system energies after the application of the measurement protocol, P j can be written as…”

Section: Analytic γ In the Case Of H = Hnvmentioning

confidence: 99%

Autonomous dissipative Maxwell's demon in a diamond spin qutrit

Hernández-Gómez,

Gherardini,

Staudenmaier

et al. 2021

Preprint

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Engineered dynamical maps that combine not only coherent, but also unital and dissipative transformations of quantum states, have demonstrated a number of technological applications, and promise to be a beneficial tool also in quantum thermodynamic processes. Here, we exploit control of a spin qutrit to investigate energy exchange fluctuations of an open quantum system. The qutrit engineer dynamics can be understood as an autonomous feedback process, where random measurement events condition the subsequent dissipative evolution. To analyze this dynamical process, we introduce a generalization of the Sagawa-Ueda-Tasaki relation for dissipative dynamics and verify it experimentally. Not only we characterize the efficacy of the autonomous feedback protocol, but also find that the characteristic function of energy variations G(η) becomes insensitive to the process details at a single specific value of its argument. This allows us to demonstrate that a fluctuation theorem of the Jarzynski type holds for this general dissipative feedback dynamics, while previous relations were limited to unital dynamics. Moreover, in addition to the feedback efficacy, we find a witness of unitality associated with the fixed point of the dynamics.

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Quantum-Heat Fluctuation Relations in Three-Level Systems Under Projective Measurements

Cited by 12 publications

References 49 publications

Experimental verification of fluctuation relations with a quantum computer

Experimental verification of fluctuation relations with a quantum computer

Thermalization processes induced by quantum monitoring in multi-level systems

Autonomous dissipative Maxwell's demon in a diamond spin qutrit

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