# Patrick Potts

*I have also published under the name Patrick P. Hofer*

## Brief:

I am a Postdoc in the Mesoscopic Physics Group, working on quantum thermodynamics. In particular, I am interested in understanding the influence of fluctuations, measurements, and feedback on quantum thermal machines such as heat engines and refrigerators.

Go to page of Mesoscopic Physics Group

## Short CV:

- 2018 – present Postdoc, Lund University
- 2016 – 2017 Postdoc, University of Geneva, Quantum Correlations Group
- 2013 – 2016 PhD Student, University of Geneva. Supervision: M. Büttiker, E. Sukhorukov, C. Flindt
- 2015 Visiting student at McGill University with A. Clerk
- 2010 – 2012 M Sc in Physics, University of Basel. Supervision: C. Bruder, V. Stojanović
- 2007 – 2010 B Sc in Nanosciences, University of Basel

## Research:

### Quantum Thermodynamics

Just like traditional thermodynamics, quantum thermodynamics investigates the notion of heat and temperature and their potential in performing useful tasks such as charging a battery. Taking this investigation to the quantum realm, where degrees of freedom are microscopic and fluctuations are of crucial importance, results in a variety of promising research directions.

One direction of particular practical relevance is the study of thermal machines which are designed to perform a useful task such as creating work or cooling a quantum degree of freedom. In my research, I investigate such machines by considering concrete physical implementations. In the past, this led to heat engines which are based on the wave nature of electrons [1], and the particle nature of photons [2]. In the present, I investigate the effect of fluctuations, measurement, and feedback on quantum thermal machines which will hopefully lead to novel mechanisms for harvesting thermal resources by exploiting quantum effects.

On a more fundamental level, I am interested in the opportunities and the limitations that arise when combining quantum theory with thermodynamics. This gives rise to questions such as: "How well can low temperatures be measured [3]?" and "How can we extract work from microscopic degrees of freedom [4]?".

**Key Publications:**

[1] P. P. Hofer, B. Sothmann, Phys. Rev. B** 91**, 195406 (2015)

[2] P. P. Hofer, J.-R. Souquet, A. A. Clerk, Phys. Rev. B** 93**, 041418 (2016)

[3] P. P. Hofer, J. B. Brask, N. Brunner, Quantum **3**, 161 (2019)

[4] N. Lörch, C. Bruder, N. Brunner, P. P. Hofer,*-*Quantum Sci. Technol. **3**, 035014 (2018)

### Fluctuations and Quantum Measurements

"The noise is the signal!", as famously stated by Rolf Landauer. This holds especially true in the quantum realm, when combining observables that cannot be jointly measured. While mean values can often be explained with a classical theory, the fluctuations encoded in a full probability distribution can result in experiments that have no classical explanation whatsoever. To identiry such scenarios, I introduced an experimentally accessible inequality, a violation of which rules out any classical explanation for the observed data [1].

Based on full counting statistics and the Wigner function, I have devised a general theory to describe the fluctuations of non-commuting observables in quantum systems [2]. This naturally leads to a description using quasi probabilities. Negative values in these distributions implies non-classicality and the fact that measurement outcomes can only be predicted by explicitly taking into account the measurement apparatus [2,3].

Building on these works, I continue to investigate the role of quantum fluctuations and their potential in thermal machines and quantum sensing applications.

**Key Publications:**

[1] P. P. Potts, Phys. Rev. Lett. **122**, 110401 (2019)

[2] P. P. Hofer, Quantum **1**, 32 (2017)

[3] P. P. Hofer, A. A. Clerk, Phys. Rev. Lett. **116**, 013603 (2016)

### Single-Electron Sources

Recent experimental progress on the controlled emission of coherent single electrons into electronic waveguides indicates the promising nature of such systems for quantum information processing. This has been recognized by Markus Büttiker, who envisioned the "Floquet Computer", a quantum computer based on single-electron sources.

In addition to state preparation, a high degree of control in state manipulation and detection is required to perform quantum information protocols. Important milestones in the field are therefore the certification of entanglement and the implementation of a first quantum algorithm.

While the creation of entanglement with single-electron sources is now fairly well understood [1-3], the manipulation and detection of entanglement still poses major challenges. To overcome these, I work on strategies for detecting and manipulating entanglement under the restrictions imposed by a typical experiment on single-electron sources.

**Key Publications:**

[1] P. P. Hofer, D. Dasenbrook, C. Flindt, Phys. Status Solidi B **254**, 1600582 (2017)

[2] D. Dasenbrook, J. Bowles, J. B. Brask, P. P. Hofer, C. Flindt, N. Brunner, New J. Phys. **18**, 043036 (2016)

[3] P. P. Hofer, M. Büttiker, Phys. Rev. B **88**, 241308(R) (2013)

## Publications

Retrieved from Lund University's publications database

## Publications

- 2020
- Maxwell's demon in a double quantum dot with continuous charge detection
(2020) Physical Review B

Journal article

- Maxwell's demon in a double quantum dot with continuous charge detection
- 2019
- Autonomous conversion of information to work in quantum dots
(2019) Physical Review Research

Journal article - Certifying Nonclassical Behavior for Negative Keldysh Quasiprobabilities
(2019) Physical Review Letters

Journal article - Fundamental limits on low-temperature quantum thermometry with finite resolution
(2019) Quantum

Journal article - Physical Implementations of Quantum Absorption Refrigerators
(2019) Thermodynamics in the Quantum Regime

Book chapter - Power, efficiency and fluctuations in a quantum point contact as steady-state thermoelectric heat engine
(2019) Entropy

Journal article - Thermodynamic uncertainty relations including measurement and feedback
(2019) Physical Review E

Journal article

- Autonomous conversion of information to work in quantum dots
- 2018
- Detailed Fluctuation Relation for Arbitrary Measurement and Feedback Schemes
(2018) Physical Review Letters

Journal article - Optimal work extraction from quantum states by photo-assisted Cooper pair tunneling
(2018) Quantum Science and Technology

Journal article

- Detailed Fluctuation Relation for Arbitrary Measurement and Feedback Schemes
- 2017
- Markovian master equations for quantum thermal machines : Local versus global approach
(2017) New Journal of Physics

Journal article - On-demand entanglement generation using dynamic single-electron sources
(2017) Physica Status Solidi (B) Basic Research

Journal article - Quantum Thermal Machine as a Thermometer
(2017) Physical Review Letters

Journal article - Quasi-probability distributions for observables in dynamic systems
(2017) Quantum

Journal article

- Markovian master equations for quantum thermal machines : Local versus global approach
- 2016
- Autonomous quantum refrigerator in a circuit QED architecture based on a Josephson junction
(2016) Physical Review B

Journal article - Negative Full Counting Statistics Arise from Interference Effects
(2016) Physical Review Letters

Journal article - Quantum heat engine based on photon-assisted Cooper pair tunneling
(2016) Physical Review B

Journal article - Single-electron entanglement and nonlocality
(2016) New Journal of Physics

Journal article

- Autonomous quantum refrigerator in a circuit QED architecture based on a Josephson junction
- 2015
- Electron waiting times for the mesoscopic capacitor
(2015) Physica E: Low-Dimensional Systems and Nanostructures

Journal article - Electron waiting times in coherent conductors are correlated
(2015) Physical Review B - Condensed Matter and Materials Physics

Journal article - Quantum heat engines based on electronic Mach-Zehnder interferometers
(2015) Physical Review B - Condensed Matter and Materials Physics

Journal article

- Electron waiting times for the mesoscopic capacitor
- 2014
- Mach-Zehnder interferometry with periodic voltage pulses
(2014) Physical Review B - Condensed Matter and Materials Physics

Journal article - Proposal for an ac spin current source
(2014) EPL

Journal article

- Mach-Zehnder interferometry with periodic voltage pulses
- 2013
- Emission of time-bin entangled particles into helical edge states
(2013) Physical Review B - Condensed Matter and Materials Physics

Journal article

- Emission of time-bin entangled particles into helical edge states
- 2012
- Superfluid drag of two-species Bose-Einstein condensates in optical lattices
(2012) Physical Review A (Atomic, Molecular and Optical Physics)

Journal article

- Superfluid drag of two-species Bose-Einstein condensates in optical lattices