1063-7397/05/3406- © 2005 MAIK “Nauka /Interperiodica”
Russian Microelectronics, Vol. 34, No. 6, 2005, pp. 407–409. Translated from Mikroelektronika, Vol. 34, No. 6, 2005, pp. 478–480.
Original Russian Text Copyright © 2005 by Zhilyaev.
At the present time, superconducting qubits appear
to be the most promising experimental realizations of
the qubit. Electron-beam or optical lithography is well
suited to making such structures; it allows the experi-
menter to easily change from one conﬁguration to
another, depending on the aim of research. The avail-
able superconducting realizations include a charge
qubit , Mooij’s qubit , an RF-SQUID qubit ,
and a Josephson-junction qubit . Their coherent
states are being measured. However, these models suf-
fer from some drawbacks. The charge qubit is very sus-
ceptible to the migration of imperfections in the sub-
strate, exhibiting a short decoherence time. Mooij’s
qubit requires a high degree of constancy of an applied
magnetic ﬁeld. The RF-SQUID qubit is subject to
external interference on account of its fairly large loop.
For a Josephson junction to operate as a qubit, a current
has to be passed through it, but this also generates
noise. Thus, there is still no qubit realization that would
be undoubtedly superior to the others.
In this paper, a new superconductor realization of
the qubit is proposed.
Its underlying principle is as follows. In super-
conductors, electromagnetic processes suffer little
loss of intensity if they occur below a frequency
is the Planck constant
is the superconductivity gap . It is also well
known that in the zero-dissipation case a long
Josephson junction can propagate Swihart waves of
are the inductance
and capacitance per unit length, respectively [6, 7].
The existence of these waves is conﬁrmed by exper-
Consider a resonator realized as a long Josephson
junction in the form of a tunnel barrier of thickness
sandwiched between superconducting layers whose
thicknesses are somewhat larger than the London pen-
(Fig. 1). In this structure a standing
Swihart wave can be excited whose wavelength must be
twice the length
of the junction, as follows from res-
Resonator-Based Superconducting Qubit
I. N. Zhilyaev
Institute of Microelectronics Technology and High Purity Materials, Russian Academy
of Sciences, Chernogolovka, Moscow oblast, Russia
Received July 14, 2005
—A resonator-based superconductor realization of the qubit is proposed.
Schematic diagram of a resonator realized as a long Josephson junction in which a Swihart wave is excited.