104 research outputs found
Detailed Fluctuation Relation for Arbitrary Measurement and Feedback Schemes
Fluctuation relations are powerful equalities that hold far from equilibrium.
However, the standard approach to include measurement and feedback schemes may
become inapplicable in certain situations, including continuous measurements,
precise measurements of continuous variables, and feedback induced
irreversibility. Here we overcome these shortcomings by providing a recipe for
producing detailed fluctuation relations. Based on this recipe, we derive a
fluctuation relation which holds for arbitrary measurement and feedback
control. The key insight is that fluctuations inferable from the measurement
outcomes may be suppressed by post-selection. Our detailed fluctuation relation
results in a stringent and experimentally accessible inequality on the
extractable work, which is saturated when the full entropy production is
inferable from the data.Comment: Published version. The first author was previously known as Patrick
P. Hofe
Probabilistically Violating the First Law of Thermodynamics in a Quantum Heat Engine
Fluctuations of thermodynamic observables, such as heat and work, contain
relevant information on the underlying physical process. These fluctuations are
however not taken into account in the traditional laws of thermodynamics. While
the second law is extended to fluctuating systems by the celebrated fluctuation
theorems, the first law is generally believed to hold even in the presence of
fluctuations. Here we show that in the presence of quantum fluctuations, also
the first law of thermodynamics may break down. This happens because quantum
mechanics imposes constraints on the knowledge of heat and work. To illustrate
our results, we provide a detailed case-study of work and heat fluctuations in
a quantum heat engine based on a circuit QED architecture. We find
probabilistic violations of the first law and show that they are closely
connected to quantum signatures related to negative quasi-probabilities. Our
results imply that in the presence of quantum fluctuations, the first law of
thermodynamics may not be applicable to individual experimental runs
Full counting statistics of the photocurrent through a double quantum dot embedded in a driven microwave resonator
Detection of single, itinerant microwave photons is an important
functionality for emerging quantum technology applications as well as of
fundamental interest in quantum thermodynamics experiments on heat transport.
In a recent experiment [W. Khan et al., Nat. Commun. 12, 5130 (2021)], it was
demonstrated that a double quantum dot (DQD) coupled to a microwave resonator
can act as an efficient and continuous photodetector by converting an incoming
stream of photons to an electrical photocurrent. In the experiment, average
photon and electron flows were analyzed. Here we theoretically investigate, in
the same system, the fluctuations of the photocurrent through the DQD for a
coherent microwave drive of the resonator. We consider both the low frequency
full counting statistics as well as the finite-frequency noise (FFN) of the
photocurrent. Numerical results and analytical expressions in limiting cases
are complemented by a mean-field approach neglecting dot-resonator
correlations, providing a compelling and physically transparent picture of the
photocurrent statistics. We find that for ideal, unity efficiency detection,
the fluctuations of the charge current reproduce the Poisson statistics of the
incoming photons, while the statistics for non-ideal detection is
sub-Poissonian. Moreover, the FFN provides information of the system parameter
dependence of detector short-time properties. Our results give novel insight
into microwave photon-electron interactions in hybrid dot-resonator systems and
provide guidance for further experiments on continuous detection of single
microwave photons.Comment: 16 pages, 4 figure
Stochastic thermodynamics of a quantum dot coupled to a finite-size reservoir
In nano-scale systems coupled to finite-size reservoirs, the reservoir
temperature may fluctuate due to heat exchange between the system and the
reservoirs. To date, a stochastic thermodynamic analysis of heat, work and
entropy production in such systems is however missing. Here we fill this gap by
analyzing a single-level quantum dot tunnel coupled to a finite-size electronic
reservoir. The system dynamics is described by a Markovian master equation,
depending on the fluctuating temperature of the reservoir. Based on a
fluctuation theorem, we identify the appropriate entropy production that
results in a thermodynamically consistent statistical description. We
illustrate our results by analyzing the work production for a finite-size
reservoir Szilard engine
Efficient and Continuous Microwave Photodetection in Hybrid Cavity-Semiconductor Nanowire Double Quantum Dot Diodes
Single photon detectors are key for time-correlated photon counting
applications [1] and enable a host of emerging optical quantum information
technologies [2]. So far, the leading approach for continuous and efficient
single-photon detection in the optical domain has been based on semiconductor
photodiodes [3]. However, there is a paucity of efficient and continuous
single-photon detectors in the microwave regime, because photon energies are
four to five orders of magnitude lower therein and conventional photodiodes do
not have that sensitivity. Here we tackle this gap and demonstrate how
itinerant microwave photons can be efficiently and continuously converted to
electrical current in a high-quality, semiconducting nanowire double quantum
dot that is resonantly coupled to a cavity. In particular, in our detection
scheme, an absorbed photon gives rise to a single electron tunneling event
through the double dot, with a conversion efficiency reaching 6 %. Our results
pave the way for photodiodes with single-shot microwave photon detection, at
the theoretically predicted unit efficiency [4]
Information-to-work conversion in single molecule experiments: from discrete to continuous feedback
We theoretically investigate the extractable work in single molecule
unfolding-folding experiments with applied feedback. Using a simple two-state
model, we obtain a description of the full work distribution, from discrete to
continuous feedback. The effect of the feedback is captured by a detailed
fluctuation theorem, accounting for the information aquired. We find analytical
expressions for the average work extraction as well as an experimentally
measurable bound thereof, which becomes tight in the continuous feedback limit.
We further determine the parameters for maximal power, or rate of work
extraction. While our two-state model only depends on a single, effective
transition rate, we find quantitative agreement with Monte Carlo simulations of
DNA hairpin unfolding-folding dynamics.Comment: 5 pages, 4 figures, 5 pages of supplementary informatio
Quantum Fokker-Planck Master Equation for Continuous Feedback Control
Measurement and feedback control are essential features of quantum science,
with applications ranging from quantum technology protocols to
information-to-work conversion in quantum thermodynamics. Theoretical
descriptions of feedback control are typically given in terms of stochastic
equations requiring numerical solutions, or are limited to linear feedback
protocols. Here we present a formalism for continuous quantum measurement and
feedback, both linear and nonlinear. Our main result is a quantum Fokker-Planck
master equation describing the joint dynamics of a quantum system and a
detector with finite bandwidth. For fast measurements, we derive a Markovian
master equation for the system alone, amenable to analytical treatment. We
illustrate our formalism by investigating two basic information engines, one
quantum and one classical
Microwave power harvesting using resonator-coupled double quantum dot photodiode
We demonstrate a microwave power-to-electrical energy conversion in a
resonator-coupled double quantum dot system. The system operated as a
photodiode, converts individual microwave photons to electrons tunneling
through the double dot, resulting in an electrical current flowing against the
applied voltage bias at input powers down to 1 femto-watt level. The device
attains a maximum power harvesting efficiency of 2%, with the
photon-to-electron conversion efficiency reaching 12%. We analyze the device
operation in both the linear and non-linear microwave power response regimes
and compare the results to theoretical predictions, finding good agreement.Comment: 5 pages, 3 figure
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