Ultrafast coherent control of a hole spin qubit in a germanium quantum dot

AbstractOperation speed and coherence time are two core measures for the viability of a qubit. Strong spin-orbit interaction (SOI) and relatively weak hyperfine interaction make holes in germanium (Ge) intriguing candidates for spin qubits with rapid, all-electrical coherent control. Here we report ultrafast single-spin manipulation in a hole-based double quantum dot in a germanium hut wire (GHW). Mediated by the strong SOI, a Rabi frequency exceeding 540 MHz is observed at a magnetic field of 100 mT, setting a record for ultrafast spin qubit control in semiconductor systems. We demonstrate that the strong SOI of heavy holes (HHs) in our GHW, characterized by a very short spin-orbit length of 1.5 nm, enables the rapid gate operations we accomplish. Our results demonstrate the potential of ultrafast coherent control of hole spin qubits to meet the requirement of DiVincenzo’s criteria for a scalable quantum information processor.

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Superadiabatic spin-preserving control of a single-spin qubit in a double quantum dot with spin–orbit interaction

Journal of Physics B Atomic Molecular and Optical Physics ◽

10.1088/1361-6455/ab4022 ◽

2019 ◽

Vol 52 (23) ◽

pp. 235502

Author(s):

Sergio S Gomez ◽

Rodolfo H Romero

Keyword(s):

Quantum Dot ◽

Orbit Interaction ◽

Double Quantum ◽

Spin Orbit ◽

Spin Orbit Interaction ◽

Single Spin ◽

Double Quantum Dot ◽

Spin Qubit

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An Operation Guide of Si-MOS Quantum Dots for Spin Qubits

Nanomaterials ◽

10.3390/nano11102486 ◽

2021 ◽

Vol 11 (10) ◽

pp. 2486

Author(s):

Rui-Zi Hu ◽

Rong-Long Ma ◽

Ming Ni ◽

Xin Zhang ◽

Yuan Zhou ◽

...

Keyword(s):

Quantum Dots ◽

Quantum Dot ◽

Rabi Oscillation ◽

Stability Diagram ◽

Near Neighbor ◽

Spin Qubits ◽

Orbital State ◽

Single Spin ◽

Spin Qubit ◽

Charge Stability

In the last 20 years, silicon quantum dots have received considerable attention from academic and industrial communities for research on readout, manipulation, storage, near-neighbor and long-range coupling of spin qubits. In this paper, we introduce how to realize a single spin qubit from Si-MOS quantum dots. First, we introduce the structure of a typical Si-MOS quantum dot and the experimental setup. Then, we show the basic properties of the quantum dot, including charge stability diagram, orbital state, valley state, lever arm, electron temperature, tunneling rate and spin lifetime. After that, we introduce the two most commonly used methods for spin-to-charge conversion, i.e., Elzerman readout and Pauli spin blockade readout. Finally, we discuss the details of how to find the resonance frequency of spin qubits and show the result of coherent manipulation, i.e., Rabi oscillation. The above processes constitute an operation guide for helping the followers enter the field of spin qubits in Si-MOS quantum dots.

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Intrinsic errors in transporting a single-spin qubit through a double quantum dot

Physical Review A ◽

10.1103/physreva.96.012309 ◽

2017 ◽

Vol 96 (1) ◽

Cited By ~ 10

Author(s):

Xiao Li ◽

Edwin Barnes ◽

J. P. Kestner ◽

S. Das Sarma

Keyword(s):

Quantum Dot ◽

Double Quantum ◽

Single Spin ◽

Double Quantum Dot ◽

Spin Qubit

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Fundamental limits of electron and nuclear spin qubit lifetimes in an isolated self-assembled quantum dot

npj Quantum Information ◽

10.1038/s41534-021-00378-2 ◽

2021 ◽

Vol 7 (1) ◽

Author(s):

George Gillard ◽

Ian M. Griffiths ◽

Gautham Ragunathan ◽

Ata Ulhaq ◽

Callum McEwan ◽

...

Keyword(s):

Quantum Dot ◽

Spin Relaxation ◽

Nuclear Spin ◽

Operating Conditions ◽

External Control ◽

Spin Qubits ◽

Fundamental Limits ◽

Trade Offs ◽

Wide Range ◽

Spin Qubit

AbstractCombining external control with long spin lifetime and coherence is a key challenge for solid state spin qubits. Tunnel coupling with electron Fermi reservoir provides robust charge state control in semiconductor quantum dots, but results in undesired relaxation of electron and nuclear spins through mechanisms that lack complete understanding. Here, we unravel the contributions of tunnelling-assisted and phonon-assisted spin relaxation mechanisms by systematically adjusting the tunnelling coupling in a wide range, including the limit of an isolated quantum dot. These experiments reveal fundamental limits and trade-offs of quantum dot spin dynamics: while reduced tunnelling can be used to achieve electron spin qubit lifetimes exceeding 1 s, the optical spin initialisation fidelity is reduced below 80%, limited by Auger recombination. Comprehensive understanding of electron-nuclear spin relaxation attained here provides a roadmap for design of the optimal operating conditions in quantum dot spin qubits.

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