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Title: Microwave-driven coherent operation of a semiconductor quantum dot charge qubit

An intuitive realization of a qubit is an electron charge at two well-defined positions of a double quantum dot. The qubit is simple and has the potential for high-speed operation because of its strong coupling to electric fields. But, charge noise also couples strongly to this qubit, resulting in rapid dephasing at all but one special operating point called the ‘sweet spot’. In previous studies d.c. voltage pulses have been used to manipulate semiconductor charge qubits but did not achieve high-fidelity control, because d.c. gating requires excursions away from the sweet spot. Here, by using resonant a.c. microwave driving we achieve fast (greater than gigahertz) and universal single qubit rotations of a semiconductor charge qubit. The Z-axis rotations of the qubit are well protected at the sweet spot, and we demonstrate the same protection for rotations about arbitrary axes in the X–Y plane of the qubit Bloch sphere. We characterize the qubit operation using two tomographic approaches: standard process tomography and gate set tomography. Moreover, both methods consistently yield process fidelities greater than 86% with respect to a universal set of unitary single-qubit operations.
Authors:
 [1] ;  [1] ;  [1] ;  [2] ;  [2] ;  [2] ;  [1] ;  [1] ;  [1] ;  [1] ;  [1]
  1. Univ. of Wisconsin, Madison, WI (United States)
  2. Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
Publication Date:
OSTI Identifier:
1182978
Report Number(s):
SAND--2014-15683J
Journal ID: ISSN 1748-3387; 533644
Grant/Contract Number:
AC04-94AL85000
Type:
Accepted Manuscript
Journal Name:
Nature Nanotechnology
Additional Journal Information:
Journal Volume: 10; Journal Issue: 3; Journal ID: ISSN 1748-3387
Publisher:
Nature Publishing Group
Research Org:
Sandia National Laboratories (SNL-NM), Albuquerque, NM (United States)
Sponsoring Org:
USDOE National Nuclear Security Administration (NNSA)
Country of Publication:
United States
Language:
English
Subject:
77 NANOSCIENCE AND NANOTECHNOLOGY quantum dots; quantum information; qubits