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Microwave Spectroscopy of a Carbon Nanotube Charge Qubit

Penfold-Fitch, ZV; Sfigakis, F; Buitelaar, MR; (2017) Microwave Spectroscopy of a Carbon Nanotube Charge Qubit. Physical Review Applied , 7 (5) , Article 054017. 10.1103/PhysRevApplied.7.054017. Green open access

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Abstract

Carbon nanotube quantum dots allow accurate control of electron charge, spin, and valley degrees of freedom in a material which is atomically perfect and can be grown isotopically pure. These properties underlie the unique potential of carbon nanotubes for quantum information processing, but developing nanotube charge, spin, or spin-valley qubits requires efficient readout techniques as well as understanding and extending quantum coherence in these devices. Here, we report on microwave spectroscopy of a carbon nanotube charge qubit in which quantum information is encoded in the spatial position of an electron. We combine radio-frequency reflectometry measurements of the quantum capacitance of the device with microwave manipulation to drive transitions between the qubit states. This approach simplifies charge-state readout and allows us to operate the device at an optimal point where the qubit is first-order insensitive to charge noise. From these measurements, we are able to quantify the degree of charge noise experienced by the qubit and obtain an inhomogeneous charge coherence of 5 ns. We use a chopped microwave signal whose duty-cycle period is varied to measure the decay of the qubit states, yielding a charge relaxation time of 48 ns.

Type: Article
Title: Microwave Spectroscopy of a Carbon Nanotube Charge Qubit
Open access status: An open access version is available from UCL Discovery
DOI: 10.1103/PhysRevApplied.7.054017
Publisher version: http://doi.org/10.1103/PhysRevApplied.7.054017
Language: English
Additional information: © 2017 American Physical Society. This version is the version of record. For information on re-use, please refer to the publisher’s terms and conditions.
Keywords: Science & Technology, Physical Sciences, Physics, Applied, Physics, DOUBLE-QUANTUM DOTS, SPIN, TRANSPORT
UCL classification: UCL > Provost and Vice Provost Offices
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > London Centre for Nanotechnology
URI: http://discovery.ucl.ac.uk/id/eprint/1561238
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