with Nanoscale Josephson Junctions
have developed two novel Josephson circuits intended as prototypes of
protected qubits whose logical states are decoupled from the environment by
encoding them in a parity of a large number. The first type, the so-called
charge-pairing qubit , represents a chain of two Josephson elements
characterized by the π periodicity of the phase dependence of their
Josephson energy (the so-called Josephson
rhombi ). The second type, the flux-pairing qubit , consists of a
4π periodic Josephson element (a Cooper
pair box with the e charge on the
central island) shunted by a superinductor . The lowest-energy quantum
states of the charge-pairing qubit are encoded in the parity of Cooper pairs
on a superconducting island flanked by the Josephson rhombi. The flux-pairing
qubit encodes its quantum states in the parity of magnetic flux quanta inside
a superconducting loop.
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Paramanandam, L.B. Ioffe, and M.E. Gershenson. Protected Josephson Rhombus
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S. Gladchenko, D. Olaya, E. Dupont-Ferrier,
B. Doucot, L.B. Ioffe, and
M.E. Gershenson. Superconducting Nanocircuits
for Topologically Protected Qubits. Nature Physics 5, 48-53 (2009).
Bell, W. Zhang, L. B. Ioffe, and M. E. Gershenson. Spectroscopic Evidence of
the Aharonov-Casher Effect in a Cooper Pair Box. Phys. Rev. Lett. 116,
Bell, I.A. Sadovskyy, L.B. Ioffe, A.Yu. Kitaev, and M.E.
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