The INSPEQT project deals with an essential hardware component of quantum computers, namely, a source of indistinguishable photons. One possible way to build a quantum computer is to use photons as quantum bits and make them interfere to perform operations.
However, an optical computer will function correctly only if all the qubits (i.e. photons) are exactly identical to each other. When this condition is fulfilled, they are said to be “indistinguishable”.
Vannucci and his team will develop new theoretical models and experimental methods to obtain indistinguishable photons from a special class of ultra-thin materials called “transition metal dichalcogenides”, with a thickness of only a few atomic layers.
The impossible made possible
Thanks to the superposition principle, a computer that uses the laws of quantum mechanics will be able to perform calculations that are impossible for even the most powerful computer in the world.
For example, a quantum computer could simulate the complex reaction mechanism that is needed to produce ammonia (the most important fertilizer in the world) or predict how certain molecules combine together to make new drugs.
This is why big companies such as Google, IBM, and Microsoft are striving to realize a fully-functioning quantum computer. In this context, Vannucci's project will improve the understanding of one of its essential components.
Perspectives
The shared vision in the field is to integrate efficient emitters of indistinguishable photons with other optical components such as waveguides and detectors. Transition metal dichalcogenides are very promising in this regard, and may offer an advantage with respect to more established materials. Due to the van der Waals nature of interlayer forces, it is rather easy to exfoliate a few atomic layers and transfer them onto different substrates. However, their performance in terms of indistinguishability is quite poor, and this is one of the most significant challenges in this field right now.
Expectations
Vannucci’s goal is to understand the physical mechanism that limits indistinguishability in these materials, and to demonstrate a way to overcome the problem. A specific issue that he wants to investigate is the role of lattice vibration of the host crystal, which may dissipate energy thereby making the photons distinguishable.
He also expects to find new solutions to initialize the emitter correctly. Any emitter is somewhat similar to an atom: if the atom is excited, it relaxes to a state with lower energy by emitting a photon. While the process of spontaneous emission is very well understood, it is quite challenging to prepare the emitter in the required excited state with a fast and reliable process.
Sapere Aude
“I am delighted to receive this prestigious grant from DFF” Vannucci says, continuing “I consider this an important professional achievement and a huge opportunity, which will give me full freedom to pursue my research objectives and explore fascinating phenomena”.
Thanks to the Sapere Aude programme, he will have the opportunity to establish and lead his own team composed by a PhD student, a Postdoc, and himself, and to collaborate with other excellent researchers both in Denmark and abroad.
