7 research outputs found
Implementation of low-loss superinductances for quantum circuits
The simultaneous suppression of charge fluctuations and offsets is crucial
for preserving quantum coherence in devices exploiting large quantum
fluctuations of the superconducting phase. This requires an environment with
both extremely low DC and high RF impedance. Such an environment is provided by
a superinductance, defined as a zero DC resistance inductance whose impedance
exceeds the resistance quantum at
frequencies of interest (1 - 10 GHz). In addition, the superinductance must
have as little dissipation as possible, and possess a self-resonant frequency
well above frequencies of interest. The kinetic inductance of an array of
Josephson junctions is an ideal candidate to implement the superinductance
provided its phase slip rate is sufficiently low. We successfully implemented
such an array using large Josephson junctions (), and measured
internal losses less than 20 ppm, self-resonant frequencies greater than 10
GHz, and phase slip rates less than 1 mHz
Evidence for coherent quantum phase-slips across a Josephson junction array
Superconducting order in a sufficiently narrow and infinitely long wire is
destroyed at zero temperature by quantum fluctuations, which induce
slips of the phase of the order parameter. However, in a finite-length wire
coherent quantum phase-slips would manifest themselves simply as shifts of
energy levels in the excitations spectrum of an electrical circuit
incorporating this wire. The higher the phase-slips probability amplitude, the
larger are the shifts. Phase-slips occurring at different locations along the
wire interfere with each other. Due to the Aharonov-Casher effect, the
resulting full amplitude of a phase-slip depends on the offset charges
surrounding the wire. Slow temporal fluctuations of the offset charges make the
phase-slips amplitudes random functions of time, and therefore turn energy
levels shifts into linewidths. We experimentally observed this effect on a long
Josephson junction array acting as a "slippery" wire. The slip-induced
linewidths, despite being only of order 100 kHz, were resolved from the
flux-dependent dephasing of the fluxonium qubit.Comment: 15 page
Reaching 10 ms single photon lifetimes for superconducting aluminum cavities
Three-dimensional microwave cavities have recently been combined with
superconducting qubits in the circuit quantum electrodynamics (cQED)
architecture. These cavities should have less sensitivity to dielectric and
conductor losses at surfaces and interfaces, which currently limit the
performance of planar resonators. We expect that significantly (>10^3) higher
quality factors and longer lifetimes should be achievable for 3D structures.
Motivated by this principle, we have reached internal quality factors greater
than 0.5x10^9 and intrinsic lifetimes of 0.01 seconds for multiple aluminum
superconducting cavity resonators at single photon energies and millikelvin
temperatures. These improvements could enable long lived quantum memories with
submicrosecond access times when strongly coupled to superconducting qubits.Comment: 4 pages, 2 figure