INTRIQ Seminar

Interfacing dopants with CMOS transistors and superconducting circuits for quantum information processing

Eva Dupont-Ferrier

Université de Sherbrooke

Dopants in silicon are promising candidates for quantum information processing. They form an extremely compact and reproducible quantum system in which the nuclear spin can be used to store quantum information, while the electron spin serves as a means of interfacing the nuclear spin with other quantum systems. The nuclear spin in purified silicon has set the record for coherence times in solid state qubits [1] and spin readout and manipulation for both electron and nuclear spins have been demonstrated, with fidelities beyond the threshold for quantum error correction protocols [2]. But high coherence times come in pair with strong isolation from the environment, i.e. spins of dopants are difficult to address and couple together which hinders implementation of two-qubit gates.

I will show how integration of dopants in transistors from state-of-the-art CMOS technology could help solve this problem. We use a split-gate transistor to electrically control two dopants connected in series [3] and perform coherent charge exchange between them [4]. For longer-range coupling between dopants, a possibility is to use magnetic coupling of the dopants? spins to superconducting circuits. I will show the first steps in that direction, namely the realization of high quality factor superconducting resonator, tunable in frequency by means of an embedded SQUID and which can maintain high quality factor under magnetic fields [5].

[1] K. Saeedi et al. Science 342 830 (2013).
[2] A. Morello, et al. Nature 467, 687 (2010), Muhonen et al. Nature nanotechnology 9, 986 (2014).
[3] B. Roche et al. Phys. Rev. Lett. 108, 206812 (2012)
[4] E. Dupont-Ferrier et al. Phys. Rev. Lett. 110, 136802 (2013).
[5] O. Kennedy et al. Phys. Rev. App. 11, 014006 (2019).