Andrea Morello from the Centre for Quantum Computation & Communication Technology in the School of Electrical Engineering & Telecommunications at UNSW will be presenting this webinar

Dial in details are below

https://monash.zoom.us/j/89337887237?pwd=U0tLcUF3a2JlbGRHbXU5NDJWdGVxQT09

Webinar ID 893 3788 7237

Passcode 28086

Abstract

Dopant atoms in silicon are a versatile platform for experiments in quantum information processing, as well as quantum foundations. The electron [1] and nuclear [2] spin of a 31P donor were the first qubit demonstrated in silicon, and went on to become among of the most coherent qubits in the solid state, with coherence times exceeding 30 seconds [3], and quantum gate fidelities approaching 99.99% [4].

In this talk I will present the state of the art and future directions for donor spins in silicon. For quantum information, the current focus is on multi-qubit operations, scale-up and fault tolerance. We have demonstrated an exchange-based 2-qubit CROT gate for electron spins [5], using a device in which we implanted a high dose of 31P donors. Future experiments will focus on using deterministic, counted single-ion implantation, for which we have recently demonstrated the capability to detect an individual ion with 99.85% confidence [6]. With nuclear spins, we have achieved the landmark result of universal 1- and 2-qubit logic operations with >99% fidelity, and prepared a 3-qubit GHZ entangled state with 92.5% fidelity [7]. We have also demonstrated the coherent electrical control of an electron-nuclear flip-flop qubit [8], which will greatly facilitate the integration of single-atom qubits in nanoelectronic devices.

Heavier donors possess a high nuclear spin quantum number, which can be used to study quantum chaos in a single quantum system [9]. Chaotic dynamics must be understood and controlled for the correct operation of quantum computers and quantum simulators [10]. In the process of operating a single 123Sb nucleus, we (re)discovered the phenomenon of nuclear electric resonance, and applied it for the first time to a single nuclear spin [11]. This provides yet another pathway to scale up and integrate donor-based quantum technologies.

[1] J. Pla et al., Nature 489, 541 (2012)

[2] J. Pla et al., Nature 496, 334 (2013)

[3] J. Muhonen et al., Nature Nanotechnology 9, 986 (2014)

[4] J. Muhonen et al., J. Phys: Condens. Matter 27, 154205 (2015)

[5] M. Madzik et al., Nature Communications 12, 181 (2021)

[6] A. Jakob et al., Advanced Materials, doi:10.1002/adma.202103235 (2021)

[7] M. Madzik et al., Nature 601, 348 (2022)

[8] G. Tosi et al., Nature Communications 8, 450 (2017)

[9] V. Mourik et al., Physical Review E 98, 042206 (2018)

[10] L. Sieberer et al., NPJ Quantum Information 5:78 (2019)

[11] S. Asaad et al., Nature 579, 205 (2020)