Demonstrating the quantum advantage The development of quantum technologies has generated a lot of interest, with the commercial sector keen to harness their potential, for example in communication and computing. We spoke to Dr Eleni Diamanti about the QuSCo project’s work in proving the advantages of quantum technologies and bringing them closer to practical application. The difference between a classical bit and a quantum bit can be expressed through the notion of quantum superposition. While information in a classical bit is represented as either 0 or 1, a quantum bit (qubit) can exist in a space between 0 and 1. “This is the notion of superposition,” says Doctor Eleni Diamanti, CNRS Research Director in the Quantum Information team at Sorbonne University in Paris. This superposition is typically expressed in mathematical terms as a combination of 0 and 1. “We express it as a function of 0 and 1. These are quantum states, not classical bits; these are states corresponding to specific physical properties of the quantum particle,” explains Dr Diamanti. “We can express qubits using coefficients that allow to calculate the probability of finding the quantum state in either 0 or 1. This is what we mean when we say that the qubit exists in states in-between.”
Researchers nowadays have a fairly thorough understanding of how to generate and manipulate these qubits, which is central to the development of quantum technologies. The properties of qubits are used in quantum technologies to propagate and manipulate information. “These 0s and 1s correspond to information. The goal of quantum technologies is to use this particular way of using and encoding information to perform tasks that – because of the properties of these qubits – cannot be done in the classical world,” continues Dr Diamanti. Research into quantum technologies has been broken down into several main categories. “One large category is quantum communication, which is necessary to connect distant quantum systems, and whose major goal is to show that you can use quantum technologies to improve security or communication efficiency, to show an advantage in the security or the necessary amount of information transmission,” says Dr Diamanti. “A second major theme is quantum computing, where quantum technology could be used to improve computation time.”
QuSCo project
Illustration by Kevin Hong
This is a topic at the core of the QuSCo project, an initiative funded by the European Research
Council which aims at demonstrating the benefits of quantum technologies for certain applications. While these technologies hold rich potential across a range of different areas, Dr Diamanti’s primary focus is on quantum communication and quantum computing. “I have worked for many years on quantum communication, in particular quantum cryptography. This involves looking at how to use quantum states of light, in particular, to improve security in communications,” she explains. “In QuSCo, we have done some work on cryptography, and are also looking towards quantum computing as well. We aim to demonstrate a quantum advantage in certain applications, essentially to identify and implement tasks that can be done better with quantum systems than classical systems with current or near-term photonic technology.” The nature of the comparison between quantum and classical resources is an important consideration in the project, with Dr Diamanti and her colleagues striving to ensure that it is fair and balanced. While there is a lot of interest in the potential of new technologies, the aim in the project is to demonstrate the potential of existing quantum technologies in certain applications, for example in the verification of the solutions of difficult computational problems. For this, Dr Diamanti needs sequences of very
weak light signals that are detected by single-photon detectors that can perform measurements at the level of a single photon. A high degree of care must be taken when working with these types of systems, as they are characterised by many different properties. For example a photon has several properties; it is situated in time, in space, and its energy is characterised by a specific frequency. “All of these properties are attached to the photon. So when you work with specific quantum particles, and you choose which properties you are going to use for observing your quantum effects, you need to also be aware of what’s happening to the other properties,” explains Dr Diamanti. While Dr Diamanti uses sophisticated photonic techniques in her research, her primary interest in terms of the QuSCo project is more in the application level. “These techniques are tools through which I aim to demonstrate a quantum advantage at a systems level,” she says. “I work at the protocol level, and collaborate with computer scientists and mathematicians to make these protocols implementable.”
Training This can be thought of almost as a step towards a proof-of-concept, with Dr Diamanti aiming to show that this quantum advantage can bring practical benefits. Alongside the technical work, the project also brings together a team, helping the next generation of researchers gain the skills they need to push forward the development of quantum technologies. “It’s very important to train new researchers that have global knowledge in all of the fields that
are associated with quantum technology,” stresses Dr Diamanti. Continued research can help reinforce the wider relevance of quantum technologies, and encourage further investment. “This encourages us that quantum technologies do have this transformational capacity and can be used in practical, realworld applications,” says Dr Diamanti. There are many challenges to deal with before quantum technologies are more widely applied however, including not just technical issues but also around areas like standards and patents for example. For her part, Dr Diamanti plans to continue her research into quantum communication networks, with the wider aim of demonstrating the applicability of quantum technologies. “I aim to show that existing quantum technologies can bring real benefits in the near term,” she says. This is not yet widely understood, as it is commonly thought that technologies like quantum computers and a full quantum internet are still several years away, which maybe leads us to overlook recent advances. “Many people have worked on questions around quantum photonic technologies, but more needs to be done at the application level to show what this can be useful for,” continues Dr Diamanti. “My target is to show that this can be achieved with current technology, or technology that will be available in the near future, without having to wait decades for the arrival of the quantum computer.”
QUSCO Quantum superiority with coherent states Project Objectives
In this project we aim at developing a theoretical framework where quantum resources can be used to outperform their classical counterparts for a large range of problems with applications in cryptography and communication, and its implementation using a photonic experimental platform exploiting state-of-the-art, practical technologies.
Project Funding
European Research Council Starting Grant Total funding € 1 494 738.
Contact Details
Dr Eleni Diamanti Research Director at CNRS, LIP6 Sorbonne Université, 4 place Jussieu, 75252 Paris Cedex 05, France Vice Director, Paris Centre for Quantum Computing T: +33 (0)1 44 27 83 12 E: eleni.diamanti@lip6.fr W: https://www.quantuminfolip6.fr W: http://www.pcqc.fr
Dr Eleni Diamanti
Photograph by Olivier Ezratty for www.qfdn.net
Dr Eleni Diamanti is a CNRS researcher director at the LIP6 laboratory of Sorbonne University in Paris. She received her Diploma in Electrical and Computer Engineering from the National Technical University of Athens in 2000 and her PhD in Electrical Engineering from Stanford University in 2006. She then worked as a Marie Curie post-doc at the Institute of Optics Graduate School in Palaiseau before joining the CNRS in 2009. She is vice director of the Paris Centre for Quantum Computing, steering committee member of the French regional and national networks on Quantum Technologies, and elected member of the Board of Stakeholders of the European Public Private Partnership in Photonics.
We aim to demonstrate a quantum advantage in certain applications, essentially to identify and implement tasks that can be done better with quantum systems than classical systems with current or near-
term photonic technology.
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EU Research
www.euresearcher.com
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