Alain Aspect is a French physicist who was awarded the Nobel Prize in Physics in 2022 for his groundbreaking work in the field of quantum mechanics, in particular for his pioneering research into the properties of entangled particles. Aspect’s investigations illuminate quantum physics’ strangest features. His 1982 Bell’s inequalities experiment with entangled photons helped settle the 1935 Einstein-Bohr controversy. He and his former Ph.D. student, French physicist Philippe Grangier, then demonstrated wave-particle duality for a single photon. After developing laser cooling of atoms with Claude Cohen-Tannoudji (1985–1992), French physicist who shared the Nobel Prize in Physics in 1997, he shifted to atom optics, where his group revisited quantum optics landmarks with atoms instead of photons and created disordered material quantum simulators.
Throughout his career, Aspect has conducted numerous experiments that have shed light on the mysteries of the quantum world. One of his most significant contributions was his work on quantum entanglement, by which two particles can become linked together in such a way that one cannot speak of the states of each particle, only a global state for the pair. His research on entangled photons served as a foundation for the most recent advances in quantum physics and the creation of quantum computing.
“The Nobel Prize was awarded for showing the extraordinary properties of entanglement, but I worked on many other amazing quantum phenomena, including cooling atoms below the one-photon recoil,” Aspect said in an interview with EE Times Europe.
Aspect’s research on cold atoms was an example of innovative methods to cool down atoms, immobilizing and manipulating them with lasers. This method is paramount for the achievement of neutral-atom quantum computing. His research also led to Grangier developing optical tweezers for single atoms.
Alain Aspect Physics Nobel Prize Winner 2022
Physics laureate Alain Aspect showing his Nobel Prize medal after the award ceremony on Dec. 10, 2022 (Photo: Nanaka Adach; Source: nobelprize.org)
“I think photons are very good for producing random-number–generator atoms and other processing involving a few qubits,” Aspect said. “The main advantage of the neutral atoms scheme of Antoine Browaeys used in Pasqal is the possibility of a 3D structure, which means scaling can be easily achieved.”
Professor Aspect’s research clearly demonstrated entanglement between two distinct photons by violating Bell inequalities. Each component of an entangled object is strongly linked to the other parts, even though they are separated by a distance that prevents interaction. Entanglement is a fundamental feature of quantum objects. The second quantum revolution is driven by this idea.
“It has been demonstrated since the ’80s that when you want to have a really fundamentally quantum phenomena, you need to be able to address single quantum objects and not an ensemble of objects that you control only collectively,” Aspect said.
Quantum computing aims to overcome the limitations of classical computing and bring unprecedented processing power to solve real-world problems that could not be addressed before. According to Aspect, there are currently two main challenges with quantum computing. The first one is decoherence, mainly related to the shielding and cooling of atoms. The other challenge is the possibility of entangling, at will, any site with any other site. However, he thinks there is no fundamental impossibility to solve these issues; it’s only a matter of engineering and good ideas.
Quantum computing technology will improve steadily, Aspect said. It’s like the learning curve you can find in many industrial applications.
“Let’s take the laser as an example,” he said. “Having lasers good enough for most applications took several decades. I have no doubt that when the need is here, and when no fundamental law of physics tells us that it is not possible, it’s a matter of engineering. If you have a market, and if you can invest money, it should work sooner or later, not necessarily as it was envisaged. Even at that stage, one needs flexibility.”
Aspect, who is also co-founder of Pasqal, the first quantum computing company whose co-founder won a Nobel Prize, believes we should have relevant applications of quantum simulation in the not-too-distant future. The first one is related to optimization problems, like the balancing of the electric grid. This issue is becoming increasingly relevant, as we will need to balance, at any moment, the power absorbed by electric-vehicle charging stations with the network demand. It is similar to the traveling salesman problem, wherein the complexity explodes exponentially with the number of nodes.
Pasqal
Quantum processors can be built on a variety of platforms, including trapped ions, superconducting circuits, quantum dots and neutral atoms. French startup Pasqal is working on its neutral-atom quantum computing platform to deliver a 1,000-qubit quantum computer by 2024.
Pasqal is a spinoff from the Institut d’Optique, co-founded in 2019 by Georges-Olivier Reymond, Christophe Jurczak, Aspect, Antoine Browaeys and Thierry Lahaye.
Pasqal uses a single laser, which is then split into several laser beams. That means this solution is highly scalable, as it allows the control of hundreds of qubits. The quality of the quantum operation is directly related to the quality of the laser beam, in terms of frequency stabilization, for example. They are using the best laser for implementing some stabilization techniques to guarantee this high efficiency of the quantum operation.
Cryptography
Another important application is quantum cryptography. As Aspect pointed out, “The problem with quantum cryptography is that we need quantum repeaters, as beyond a few tens of kilometers, the signal becomes weak. To have good quantum repeaters, we need good quantum memories. Once again, I think no fundamental law of physics says it will be impossible to develop good quantum memories, so we will have some sooner or later.”
Quantum physics offers an information-theoretically secure method with quantum key distribution that allows two remote parties to securely generate secret material.
Thinking about the future of quantum computing, Aspect said we need not only good physicists and engineers but also good computer scientists. Quantum physics is difficult and mostly studied in universities or public research centers. On the other hand, the industry wants to enter the game, and we must train the corresponding experts.
Quantum computing technology has advanced over the past five years and is projected to advance even further over the next five years. Quantum will predominantly augment existing computers and will rarely replace them. New quantum technology will swiftly advance, and novel applications will be created. In a few years, as technology deployment intensifies, hybrid systems comprised of classical and quantum computers will emerge. Simulations of chemistry may be the application in which quantum computers have the greatest impact. This includes applications like medical discoveries and battery technology advancements.
Partnerships between industry and academia in quantum computing will facilitate a transition from simplified adoption of advanced quantum programming to execution on quantum machines.
This gives researchers and educators crucial insights into the design of quantum applications for the future’s fault-tolerant quantum computers. Future collaborations will provide researchers and educators with the tools and resources necessary to accelerate their quantum computing research and education initiatives.
“For almost all my life, I have done basic research,” Aspect said. “Now, getting close to the end of my life, I must admit that if there are applications of that fundamental research, it is the best thing that could happen to me. That would be a good additional reward to my life.”