Zenith Grant Awardee

Natalia Ares

University of Oxford

Co-Investigators

Alexia Auffèves, Institut Neel – CNRS; Juan Parrondo, Universidad Complutense de Madrid; Owen Maroney, University of Oxford; Janet Anders, University of Exeter

Project Title

Nanomechanics in the solid-state for quantum information thermodynamics (NanoQIT)

Project Summary

The theory of thermodynamics, commonly associated with the steam engines of the 19th century, is a universal set of laws that governs everything from black holes to the evolution of life. Albert Einstein was convinced it was the only theory likely to “never be overthrown.”

This theory introduced the foundational concept of information to physics. With the recent emergence of modern technologies for the fabrication of electronic devices on the atomic scale, we can now test the link between thermodynamics and information in the quantum realm for the first time. We will fabricate devices at nanometre scales, merely a dozen atoms across, and hold them at temperatures far colder than even deepest outer space. Here quantum rather than classical laws will apply, and so we can explore the link between information and thermodynamics in the quantum world. In the same way that thermodynamics was key to building classical steam engines, the emergence of quantum machines is forcing us to reimagine this theory in the quantum realm. The time is right to dive into this unexplored field.

Maxwell’s demon, born in 1867, revealed the classical relationship between entropy and information and still thrives in modern physics. This intelligent agent had information about the velocities and positions of the particles in a gas, and could therefore transfer the fast, hot particles from a cold reservoir to a hot one, in apparent violation of the second law of thermodynamics. This finding exposed the necessity to refine the second law of thermodynamics to incorporate information explicitly, as well as to clarify the physical nature of information.

In the quantum world, the classical connection between information and thermodynamics has to be revised. We will build an experimental platform with direct access to thermodynamic quantities to explore information thermodynamics in small devices operating in the quantum regime. Controlling thermodynamic quantities at such small scales requires devices with enough sophistication to replicate the operation of a heat engine. Our devices will allow us to build machines in which the “steam” is one or two electrons, and the piston is a tiny semiconductor wire in the form of a carbon nanotube (Fig.1). We expect that exploring this new territory will have as great a fundamental impact on how we think of information as previous studies in the classical regime have had. We are excited to exploit our devices with unique capabilities to discover the singularities of quantum thermodynamics.

Technical Abstract

Quantum information thermodynamics studies the links between information, entropy and energy in a regime when fluctuations are important and quantum effects arise. This emerging field has remained mostly theoretical and it is our purpose to bring it to a new era, developing a new experimental platform based on nanoelectromechanical devices. This platform will allow us to directly measure the work done on a quantum system, store it and reuse it (Fig. 1). All classical experiments and most quantum experiments have inferred the work associated with thermodynamic process indirectly. Direct measurement of mechanical work is key to future experimental advances in quantum thermodynamics.

This project leverages our recent achievements in optomechanics with carbon nanotubes, combining electronic quantum states with fast and sensitive cavity readout of mechanical motion. These offer unique capabilities for information thermodynamics: (i) they can encode a bit of information in a system that supports quantum states, (ii) they benefit from the development of semiconductor qubit devices (iii) they finally integrate the ‘piston’, the mechanical element that allows for direct access to thermodynamic quantities and it is able to store and transfer energy.

Our overall aim is to determine the value of information as fuel, achieving unprecedented access to the particularities of thermodynamics at the nanoscale. We shall exploit the unique capabilities of our platform to: (i) demonstrate reversible work extraction cycles at the single-bit level, (ii) develop protocols for a solid-state quantum engine, and (iii) measure the fuel value of quantum information.

Realising these experiments, while now within reach, remains challenging due to the sophistication of the devices and control protocols, and the fast and sensitive measurements that are required. The project is ambitious but its feasibility is based on recent technical advances at the PI’s laboratory, introducing a novel experimental platform, and on the perfect combination of skills of the team.

The ground-breaking experiments we propose will benefit from strong support in philosophy and theory, our consortium gathering experts that have extensively studied thermodynamic reversibility in quantum information processing, the properties of quantum thermal machines and quantum Szilard engines, and that have made pioneering proposals revealing the potential of optomechanical systems for quantum thermodynamic experiments. Our experiments will inform philosophical studies investigating basic concepts of reality linked to the relationship between quantum information and entropy. With the team’s expertise spanning philosophy, experiments in semiconductor hybrid devices and theory, the PI will form and lead a group with the necessary breadth of capabilities to tackle the complex challenges ahead. This project will be key in the PI’s career advancement, resourcing her to develop a fully independent laboratory.

Our exploration of information thermodynamics in the quantum arena will inform the study of biomotors and the construction of autonomous quantum machines that might use information as fuel. It will open entirely novel lines of scientific enquiry, such as the development of engines, which by harnessing statistical fluctuations might require less stringent preservation of coherence.