764 research outputs found
Synthesis of linear, double chain, ladder polymers from substituted tetraphosphonitriles Quarterly report, Sep. - Nov. 1966
Synthesis of linear, double chain ladder polymers from substituted tetraphosphonitrile
Synthesis of linear, double chain, ladder polymers from substituted tetraphosphonitriles Quarterly progress report, Sep. - Nov. 1966
Synthesis of linear, double chain, ladder polymers from substituted tetraphosphonitrile
Cavity-assisted quantum bath engineering
We demonstrate quantum bath engineering for a superconducting artificial atom
coupled to a microwave cavity. By tailoring the spectrum of microwave photon
shot noise in the cavity, we create a dissipative environment that autonomously
relaxes the atom to an arbitrarily specified coherent superposition of the
ground and excited states. In the presence of background thermal excitations,
this mechanism increases the state purity and effectively cools the dressed
atom state to a low temperature
Quantum State Sensitivity of an Autoresonant Superconducting Circuit
When a frequency chirped excitation is applied to a classical high-Q
nonlinear oscillator, its motion becomes dynamically synchronized to the drive
and large oscillation amplitude is observed, provided the drive strength
exceeds the critical threshold for autoresonance. We demonstrate that when such
an oscillator is strongly coupled to a quantized superconducting qubit, both
the effective nonlinearity and the threshold become a non-trivial function of
the qubit-oscillator detuning. Moreover, the autoresonant threshold is
sensitive to the quantum state of the qubit and may be used to realize a high
fidelity, latching readout whose speed is not limited by the oscillator Q.Comment: 5 pages, 4 figure
1/f noise of Josephson-junction-embedded microwave resonators at single photon energies and millikelvin temperatures
We present measurements of 1/f frequency noise in both linear and
Josephson-junction-embedded superconducting aluminum resonators in the low
power, low temperature regime - typical operating conditions for
superconducting qubits. The addition of the Josephson junction does not result
in additional frequency noise, thereby placing an upper limit for fractional
critical current fluctuations of (Hz) at 1 Hz for
sub-micron, shadow evaporated junctions. These values imply a minimum dephasing
time for a superconducting qubit due to critical current noise of 40 -- 1400
s depending on qubit architecture. Occasionally, at temperatures above 50
mK, we observe the activation of individual fluctuators which increase the
level of noise significantly and exhibit Lorentzian spectra
Dispersion management using betatron resonances in an ultracold-atom storage ring
Specific velocities of particles circulating in a storage ring can lead to
betatron resonances at which static perturbations of the particles' orbit yield
large transverse (betatron) oscillations. We have observed betatron resonances
in an ultracold-atom storage ring by direct observation of betatron motion.
These resonances caused a near-elimination of the longitudinal dispersion of
atomic beams propagating at resonant velocities, an effect which can improve
the performance of atom interferometric devices. Both the resonant velocities
and the strength of the resonances were varied by deliberate modifications to
the storage ring.Comment: 4 pages, 5 figures. Also available at
http://physics.berkeley.edu/research/ultracol
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