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Review of Scientific Instruments / Volume 75 / Issue 8 / ARTICLES / ELECTRONICS; ELECTROMAGNETIC TECHNOLOGY; MICROWAVES

Rev. Sci. Instrum. 75, 2541 (2004); http://dx.doi.org/10.1063/1.1771499 (4 pages)

Low-noise computer-controlled current source for quantum coherence experiments

S. Linzen, T. L. Robertson, T. Hime, B. L. T. Plourde, P. A. Reichardt, and John Clarke

Department of Physics, University of California, Berkeley, California 94720-7300

(Received 10 February 2004; accepted 2 May 2004; published online 26 July 2004)

We describe a dual current source designed to provide static flux biases for a superconducting qubit and for the Superconducting QUantum Interference Device (SQUID) which measures the qubit state. The source combines digitally programmable potentiometers with a stabilized voltage source. Each channel has a maximum output of ±1 mA, and can be adjusted with an accuracy of about ±1 nA. Both current supplies are fully computer controlled and designed not to inject digital noise into the quantum bit and SQUID during manipulation and measurement of the flux. For a 275 μA setting, the measured noise current is 2.6 parts per million (ppm) rms, in a bandwidth of 0.0017–10 Hz, from which we estimate dephasing times of hundreds of nanoseconds in the particular case of our own qubit design. By resetting the current every 10 min, we are able to reduce the drift to no more than 5 ppm at a current of 750 μA over a period of 3 days. The current source has been implemented without thermal regulation inside a radiofrequency-shielding room, and is used routinely in our quantum coherence experiments.

© 2004 American Institute of Physics.

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KEYWORDS and PACS

Keywords

constant current sources, SQUIDs, quantum noise, mesoscopic systems, potentiometers

PACS

  • 85.25.Dq

    Superconducting quantum interference devices (SQUIDs)

  • 84.30.Jc

    Power electronics; power supply circuits

ARTICLE DATA

Digital Object Identifier
http://dx.doi.org/10.1063/1.1771499

PUBLICATION DATA

ISSN

0034-6748 (print)  
1089-7623 (online)

Publisher

$abstract.society.value is a Member of CrossRef American Institute of Physics.

For access to fully linked references, you need to log in.
    Y. Makhlin, G. Schön, and A. Shnirman, Rev. Mod. Phys. 73, 357 (2001).


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