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Details of Grant 

EPSRC Reference: EP/P034012/1
Title: Hot-electron quantum optics (HEQO)
Principal Investigator: Emary, Dr C
Other Investigators:
Researcher Co-Investigators:
Project Partners:
National Physical Laboratory
Department: Sch of Maths, Statistics and Physics
Organisation: Newcastle University
Scheme: Standard Research
Starts: 02 October 2017 Ends: 01 October 2020 Value (£): 252,481
EPSRC Research Topic Classifications:
Condensed Matter Physics Quantum Optics & Information
EPSRC Industrial Sector Classifications:
Communications Electronics
Related Grants:
Panel History:
Panel DatePanel NameOutcome
25 Apr 2017 EPSRC Physical Sciences - April 2017 Announced
Summary on Grant Application Form
Quantum optics is a field of research that employs quantum-mechanics to investigate phenomena involving light and its interactions with matter. Some of the deepest results in quantum mechanics have been revealed within the framework of quantum optics, and it is also here that some of the most promising quantum-technology applications, such as quantum communication and cryptography, are being developed.

Workers in solid-state physics have long dreamt of performing their own version of quantum optics in which photons of light are replaced by electrons in a semiconductor. The ultimate goal is to understand and to be able to manipulate the quantum, wave-like properties of the electron, at the same level as we do for photons. From a technological point of view, this is important because electronic components keep getting smaller and, for this to continue, quantum effects will have to be taken into account. Moreover, by harnessing quantum effects we open the doors for new quantum technologies and, from the point of view of integration with conventional technology, semiconductors are ideal for this.

Experimentalists have succeeded in realising a number of nano-electronic circuits that emulate key photonic-quantum-optics experiments, such as the Mach-Zehnder interferometer, that show the wave-like properties of electrons. Whilst these experiments clearly demonstrate the analogy between electron and photon optics, significant differences emerge, most notably because electrons interact with one another whereas photons do not, and because of background electrons that are always present in semiconductors. Unfortunately, in a process known as decoherence, interactions between electrons tend to erase the very signatures of quantum mechanics that we are interested in. This limits the size and complexity of the electron quantum optics set-ups that we can usefully construct.

We believe that recent experiments on quantum-dot charge pumps suggest a way round this problem, and it is the aim of this project to investigate this possibility.

Charge pumps inject electrons one-by-one into the semiconductor. These electrons are then confined by a magnetic field in so-called edge-channels, which act as one-dimensional ``wires'' that carry the electrons around the circuit. The energy of the electrons emitted by the quantum-dot charge pumps we are interested in is particularly high, and this tends to push the electrons out into the edges of the semiconductor and away from the background electrons. This effect can be further enhanced by adding electrical contacts near the edges. The result is that these ''hot'', i.e. high-energy, electrons become well isolated in the edges, well away from all other electrons. This situation then closely resembles the naturally-isolated nature of photons and this, we hypothesise, will drastically reduce the problem of decoherence.

The limits on quantum effects for these hot electrons will therefore not be set by electron-electron interactions, but rather by different mechanisms. In this project we will investigate these mechanisms, isolate the important ones, and devise ways to minimise their negative effects. We will also develop software to simulate realistic hot-electron quantum-optics geometries which will give a detailed understanding of the dynamics of hot electrons in experimentally-relevant devices.

This work will be conducted in close collaboration with the experimental group of M. Kataoka at the National Physical Laboratory, who are experts in the construction and measurement of charge-pump sources. In this way we shall advance the field of electron quantum optics both theoretically and experimentally, and have impact on the most-promising application of these pumps, that as a reference for high-precision electrical measurements.

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