Towards Coupling a Superconducting Qubit to a Single Spin

Contact: Patrice Bertet,, +33 1 69 08 55 29

The goal of the internship is to couple individual spins in solids to a superconducting quantum bit for quantum computing purposes.

Full description:
Quantum Information aims at realizing a new type of computer, based on registers of two-level systems (the qu-bits) whose quantum state can be manipulated according to precise algorithms in order to solve problems otherwise untractable by classical machines, thanks to the massive parallelism offered by the quantum-mechanical superposition principle.

Spins in solids are ideal candidates for implementing such a quantum computer, because they are natural two-level systems with a very long coherence time (that can reach one second, or even one hour in certain cases) when embedded in a very pure crystalline matrix. The biggest challenge, unsolved for now on, is to couple several of these spin qubits in order to realize non-trivial quantum logic operations. In the framework of an ERC project, we are exploring an ambitious idea, which consists in coupling each spin to a superconducting circuit that would then mediate the interaction between distant spins. The first step consists in coupling one superconducting circuit called the “flux-qubit” [1] to a single spin, implemented by a NV center in diamond. For that the flux-qubit circuit will be fabricated directly on top of an ultra-pure diamond crystal, made out of isotopically-enriched Carbon 12 material, in which a NV center has been located with nanometric precision.

[1] Stern, M. et al., Phys. Rev. Lett. 113, 123601 (2014)

Experimental Techniques : clean-room techniques (optical and e-beam lithography, fabrication of tunnel junctions, all available in-house), optical detection and characterization of individual NV centers (confocal microscope), low-temperature cryogenics (20mK), ultra-low-noise microwave measurements

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