# Patrick P. PottsUniversity of Basel | UNIBAS · Department of Physics

Patrick P. Potts

Ph.D. in Physics

## About

54

Publications

6,691

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1,333

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Introduction

Patrick P. Potts (formerly Hofer) is leading the Quantum Thermodynamics Group in Basel, Switzerland. Patrick does research on Open Quantum Systems with a focus on Quantum Thermodynamics, Fluctuations, and , Non-classical Effects.

Additional affiliations

January 2018 - present

November 2016 - December 2017

January 2015 - December 2015

## Publications

Publications (54)

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 n...

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 shortcom...

We introduce an experimental test for ruling out classical explanations for the statistics obtained when measuring arbitrary observables at arbitrary times using individual detectors. This test requires some trust in the measurements, represented by a few natural assumptions on the detectors. In quantum theory, the considered scenarios are well cap...

Thermodynamic uncertainty relations quantify how the signal-to-noise ratio of a given observable is constraint by dissipation. Using an intimate connection to fluctuation relations, we extend thermodynamic uncertainty relations to scenarios which include measurement and feedback. Since measurement and feedback generally breaks time-reversal invaria...

We theoretically investigate work extraction from quantum states via an engine. The latter consists of a superconducting circuit, where a LC-resonator is coupled to a Josephson junction. The oscillator state fuels the engine, providing energy absorbed by Cooper pairs, thus producing work in the form of an electrical current against an external volt...

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...

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...

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...

Markovian master equations provide a versatile tool for describing open quantum systems when memory effects of the environment may be neglected. As these equations are of an approximate nature, they often do not respect the laws of thermodynamics when no secular approximation is performed in their derivation. Here we introduce a Markovian master eq...

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...

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 informatio...

Converting incoming photons to electrical current is the key operation principle of optical photodetectors and it enables a host of emerging quantum information technologies. The leading approach for continuous and efficient detection in the optical domain builds on semiconductor photodiodes. However, there is a paucity of efficient and continuous...

Markovian master equations provide a versatile tool for describing open quantum systems when memory effects of the environment may be neglected. As these equations are of an approximate nature, they often do not respect the laws of thermodynamics when no secular approximation is performed in their derivation. Here we introduce a Markovian master eq...

Nanoscale heat engines are subject to large fluctuations which affect their precision. The thermodynamic uncertainty relation (TUR) provides a trade-off between output power, fluctuations, and entropic cost. This trade-off may be overcome by systems exhibiting quantum coherence. This Letter provides a study of the TUR in a prototypical quantum heat...

Nanoscale heat engines are subject to large fluctuations which affect their precision. The Thermodynamic Uncertainty Relation (TUR) provides a trade-off between output power, fluctuations and entropic cost. This trade-off may be overcome by systems exhibiting quantum coherence. This letter provides a study of the TUR in a prototypical quantum heat...

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...

Thermal machines perform useful tasks, such as producing work, cooling, or heating by exchanging energy, and possibly additional conserved quantities such as particles, with reservoirs. Here we consider thermal machines that perform more than one useful task simultaneously, terming these hybrid thermal machines. We outline their restrictions impose...

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 effic...

Precise thermometry is of wide importance in science and technology in general and in quantum systems in particular. Here, we investigate fundamental precision limits for thermometry on cold quantum systems, taking into account constraints due to finite measurement resolution. We derive a tight bound on the optimal precision scaling with temperatur...

Thermal machines perform useful tasks--such as producing work, cooling, or heating--by exchanging energy, and possibly additional conserved quantities such as particles, with reservoirs. Here we consider thermal machines that perform more than one useful task simultaneously, terming these "hybrid thermal machines". We outline their restrictions imp...

We consider a scheme for on-demand teleportation of a dual-rail electron qubit state, based on single-electron sources and detectors. The scheme has a maximal efficiency of 25%, which is limited both by the shared entangled state as well as the Bell-state measurement. We consider two experimental implementations, realizable with current technology....

Converting information into work has, during the past decade, gained renewed interest as it gives insight into the relation between information theory and thermodynamics. Here, we theoretically investigate an implementation of Maxwell's demon in a double quantum dot and demonstrate how heat can be converted into work using only information. This is...

We consider a scheme for on-demand teleportation of a dual-rail electron qubit state, based on single-electron sources and detectors. The scheme has a maximal efficiency of 25%, which is limited both by the shared entangled state as well as the Bell-state measurement. We consider two experimental implementations, realizable with current technology....

Precise thermometry is of wide importance in science and technology in general and in quantum systems in particular. Here, we investigate fundamental precision limits for thermometry on cold quantum systems, taking into account constraints due to finite measurement resolution. We derive a tight bound on the optimal precision scaling with temperatur...

Converting information into work has during the last decade gained renewed interest as it gives insight into the relation between information theory and thermodynamics. Here we theoretically investigate an implementation of Maxwell's demon in a double quantum dot and demonstrate how heat can be converted into work using only information. This is ac...

Thermodynamic uncertainty relations quantify how the signal-to-noise ratio of a given observable is constrained by dissipation. Fluctuation relations generalize the second law of thermodynamics to stochastic processes. We show that any fluctuation relation directly implies a thermodynamic uncertainty relation, considerably increasing their range of...

We consider an autonomous implementation of Maxwell's demon in a quantum dot architecture acting on a system without changing its number of particles or its energy. As in the original thought experiment, only the second law of thermodynamics is seemingly violated when disregarding the demon. The autonomous architecture allows us to compare descript...

The trade-off between large power output, high efficiency and small fluctuations in the operation of heat engines has recently received interest in the context of thermodynamic uncertainty relations (TURs). Here we provide a concrete illustration of this trade-off by theoretically investigating the operation of a quantum point contact (QPC) with an...

We consider an autonomous implementation of Maxwell's demon in a quantum dot architecture. As in the original thought experiment, only the second law of thermodynamics is seemingly violated when disregarding the demon. The autonomous architecture allows us to compare descriptions in terms of information to a more traditional, thermoelectric charact...

The theory of quantum thermodynamics investigates how the concepts of heat, work, and temperature can be carried over to the quantum realm, where fluctuations and randomness are fundamentally unavoidable. Of particular practical relevance is the investigation of quantum thermal machines: Machines that use the flow of heat in order to perform some u...

The trade-off between large power output, high efficiency and small fluctuations in the operation of heat engines has recently received interest in the context of thermodynamic uncertainty relations (TURs). Here we provide a concrete illustration of this trade-off by theoretically investigating the operation of a quantum point contact (QPC) with an...

The trade-off between large power output, high efficiency and small fluctuations in the operation of heat engines has recently received interest in the context of thermodynamic uncertainty relations (TURs). Here we provide a concrete illustration of this trade-off by theoretically investigating the operation of a quantum point contact (QPC) with an...

Von Neumann measurements can be described naturally in terms of the Keldysh quasi-probability distribution (KQPD), and the imprecision and backaction exerted by the measurement apparatus. Here we introduce a classical (hidden-variable) model for von Neumann measurements. Under a few natural assumptions, we derive an experimentally accessible inequa...

Fluctuation theorems 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 shortcomi...

Absorption refrigerators are autonomous thermal machines that harness the spontaneous flow of heat from a hot bath into the environment in order to perform cooling. Here we discuss quantum realizations of absorption refrigerators in two different settings: namely, cavity and circuit quantum electrodynamics. We first provide a unified description of...

Absorption refrigerators are autonomous thermal machines that harness the spontaneous flow of heat from a hot bath into the environment in order to perform cooling. Here we discuss quantum realizations of absorption refrigerators in two different settings: namely, cavity and circuit quantum electrodynamics. We first provide a unified description of...

The study of quantum thermal machines, and more generally of open quantum systems, often relies on master equations. On the one hand, there is the widely used, but often criticized, local approach, where machine sub-systems locally couple to thermal baths. On the other hand, in the more established global approach, thermal baths couple to global de...

We propose the use of a quantum thermal machine for low-temperature thermometry. A hot thermal reservoir coupled to the machine allows for simultaneously cooling the sample while determining its temperature without knowing the model-dependent coupling constants. In its most simple form, the proposed scheme works for all thermal machines which perfo...

We consider the Keldysh quasi-probability distribution (KQPD) to describe dynamic systems. This distribution provides a measurement-independent description of the observables of interest and their time-evolution. Nevertheless, positive probability distributions for measurement outcomes can be obtained from the KQPD by taking into account the effect...

An implementation of a small quantum absorption refrigerator in a circuit QED architecture is proposed. The setup consists of three harmonic oscillators coupled to a Josephson unction. The refrigerator is autonomous in the sense that it does not require any external control for cooling, but only thermal contact between the oscillators and heat bath...

We theoretically investigate questions regarding the controlled emission and entanglement of individual electrons in mesoscopic circuits, the statistics of current fluctuations and electron waiting times for phase-coherent quantum transport, and thermal machines such as heat engines and refrigerators at the nano-scale. Chapter 2 focuses on dynamic...

We review our recent proposals for the on-demand generation of entangled few-electron states using dynamic single-electron sources. The generation of entanglement can be traced back to the single-electron entanglement produced by quantum point contacts acting as electronic beam splitters. The coherent partitioning of a single electron leads to enta...

Motivated by recent progress in electron quantum optics, we revisit the
question of single-electron entanglement, specifically whether the state of a
single electron in a superposition of two separate spatial modes should be
considered entangled. We first discuss a gedanken experiment with
single-electron sources and detectors, and demonstrate dete...

We propose and analyze a simple mesoscopic quantum heat engine that exhibits
both high-power and high-efficiency. The system consists of a biased Josephson
junction coupled to two microwave cavities, with each cavity coupled to a
thermal bath. Resonant Cooper pair tunnelling occurs with the exchange of
photons between cavities, and a temperature di...

The Keldysh-ordered full counting statistics is a quasi-probability
distribution describing the fluctuations of a time-integrated quantum
observable. While it is well known that this distribution can fail to be
positive, the interpretation and origin of this negativity has been somewhat
unclear. Here, we show how the full counting statistics can be...

We evaluate the distribution of waiting times between electrons emitted by a
driven mesoscopic capacitor. Based on a wave packet approach we obtain analytic
expressions for the electronic waiting time distribution and the joint
distribution of subsequent waiting times. These semi-classical results are
compared to a full quantum treatment based on F...

We evaluate the joint distributions of electron waiting times in coherent
conductors described by scattering theory. Successive electron waiting times in
a single-channel conductor are found to be correlated due to the fermionic
statistics encoded in the many-body state. Our formalism allows us also to
investigate the waiting times between charge t...

We theoretically investigate the thermoelectric properties of heat engines
based on Mach-Zehnder interferometers. The energy dependence of the
transmission amplitudes in such setups arises from a difference in the
interferometer arm lengths. Any thermoelectric response is thus of purely
quantum mechanical origin. In addition to an experimentally es...

We investigate a Mach-Zehnder interferometer driven by a time-dependent
voltage. Motivated by recent experiments, we focus on a train of Lorentzian
voltage pulses which we compare to a sinusoidal and a constant voltage. We
discuss the visibilities of Aharonov-Bohm oscillations in the current and in
the noise. For the current, we find a strikingly d...

We propose an ac current source that can be tuned from a pure charge to a
pure spin current source. The device consists of two mesoscopic capacitors
attached to a two-dimensional strip of a topological insulator. The change from
charge to spin current is controlled by an offset in the top gate potentials
that drive the capacitors. In addition to th...

We propose a single-particle source which emits into the helical edge states
of a two-dimensional quantum spin Hall insulator. Without breaking
time-reversal symmetry, this source acts like a pair of noiseless
single-electron emitters which each inject separately into a chiral edge state.
By locally breaking time-reversal symmetry, the source becom...

We investigate the superfluid drag that occurs between the components of a two-species
Bose-Einstein condensate in quasi two-dimensional optical lattices. This drag couples
the two different superfluid velocities in the free energy, which are used to describe such
a system. We derive an analytic expression of the drag in the limit of weak interac-...

We study two-species Bose-Einstein condensates in quasi two-dimensional
optical lattices of varying geometry and potential depth. Based on the
numerically exact Bloch and Wannier functions obtained using the plane-wave
expansion method, we quantify the drag (entrainment coupling) between the
condensate components. This drag originates from the (sho...

## Projects

Project (1)

The fields of stochastic and quantum thermodynamics generalize the theory of thermodynamics to a regime where fluctuations and measurements play a fundamental role. Powerful results have been established in these fields, including fluctuation theorems and thermodynamic uncertainty relations. Furthermore, the connection between information and entropy becomes particularly relevant on the nanoscale. This has resulted in a number of insights based on realizations of established thought experiments, such as Maxwell’s demon and Szilard’s engine.
Due to their high degree of control, small electronic systems provide ideal candidates to investigate thermodynamics on the nanoscale. In particular, all ingredients required to investigate heat and energy transport, as well as the thermodynamics of information, are available. This Special Issue aims at providing a focus on modern developments in these highly exciting topics related to energy, entropy, and information in nano- and quantum-electronics.
https://www.mdpi.com/journal/entropy/special_issues/Nano_Quantum_Electronics