Jean-Claude Besse

Jean-Claude Besse's research


I work on the fabrication of superconducting circuits, modular quantum computing processors, and quantum optics in the microwave domain using artificial atoms (see About).

Major achievement 1

In my PhD work, I led the effort on the detection [1] of individual itinerant microwave photons generated by a quantum source that we also developed and characterized [2]. This work was extended to realize a parity detector, that has been used to herald propagating cat states of microwave light [3]. A clicking detector, sensitive to parity of the incoming radiation field, may prove useful in distributed error-corrected communication protocols. We have also used the same architecture to demonstrate a universal quantum gate set on itinerant microwave photons, and realized a distinct but versatile direct source of large entangled states of microwave photons in a 1D chain [5].

[1] Single photon detection

Information is often transmitted using electromagnetic radiation, the quantum units of which are photons. In the microwave regime, detecting single itinerant photons at the receiving end of a transmission channel is challenging since microwave photons possess 5 orders of magnitude less energy than their optical counterparts. In this work, we show how to transfer the information content of a propagating photon into an excitation of a stationary qubit. By reading out the state of the latter, we acquire knowledge about the photon’s presence without destroying it. This ‘non-demolition’ aspect opens up new possibilities of detecting the photon in flight while allowing it to travel on towards another destination.

[2] Superconducting Switch

A superconducting switch, able to route quantum fields on chip with low loss, fast switching time, and high compression point. Together with it, a transmon at the end of a semi-infinite transmission line, capable of emitted single-photon Fock state with high fidelity.

[3] Parity detection

Parity is an important statistic of physical systems. Here, we go beyond single photon detection and measure the parity of radiation reflected from a detector in single shot. We showcase the parity measurement on Fock states, demonstrate direct Wigner tomography of itinerant quantum light fields, and generate Schrödinger cat states.

[4] Interacting photons

Realization of a universal quantum gate set for itinerant microwave photons, using absorption into and re-emission out of superconducting transmon qubit, combined with a photon-transmon controlled-phase gate.

[5] Entangled light modes

Quantum optics crucially relies on sources of quantum states of electromagnetic radiation. In this work, we demonstrate a source of entangled modes of microwave radiation that is fully deterministic, coherent, versatile, and scalable. Full quantum state tomography is performed up to 4 modes, and process maps of the sequential emission process allow us to find entanglement lengths of order ten photonic qubits.

Major achievement 2

I have contributed, mostly in the nano-fabrication aspects, to a multi-year long effort geared at realizing non-local microwave quantum networks. This include the deterministic remote entanglement between superconducting qubits located physically on separated quantum devices [1], the engineering of a microwave quantum link allowing these two devices to be located in separate cryogenic systems [2], and the loophole-free experimental violation of a Bell-inequality with a solid-state sytem [3].

[1] Remote entanglement

Deterministic remote entanglement between two superconducting atoms based on separate chips.

[2] Microwave Quantum Link

Remote entanglement between two superconducting chips housed in separated cryogenic systems.

[3] Loophole-free Bell test

Loophole-free violation of a Bell inequality with two superconducting circuit devices separated by a 30m-long cryogenic link.

Selcted other projects

Quantum computing aspects:

Tunable ZZ gate

A two-qubit C-PHASE gate implemented with tunable ZZ interactions.

fg-ge gate

An all-microwave gate between two far detuned superconducting qubits.

Entanglement Stabilization

Ancilla-based parity measurement, and real-time feedback, demonstrating entanglement stabilization.

Multiplexed Readout

High-fidelity, low crosstalk, fast, readout of up to 5 superconducting circuits in a multiplexed circuit.

Fundamental quantum optics:

Primary Thermometry

A primary thermometer for microwave transmission lines, requiring only a very basic setup.

2-Photon Fluorescence

A study of two-photon resonance fluorescence, and Mollow-like triplets, by driving an artificial atom at the two-photon transition between its ground and second-excited state.

Photon Ordering

A system of two driven-dissipative nonlinear resonators, showing a crossover between an ordered state and a delocalized phase of photons.

Cascade Decay

How cascade decay of a ladder-type 3-level atom leads deterministically to entangled photon pairs, that we can spatially separate.