Taking Control of Coherent Superconducting Quantum Electronics
Irfan Siddiqi
Quantum Nanoelectronics Laboratory, UC Berkeley
Electronic circuits which exhibit quantum mechanical
phenomena-superposition and entanglement, in particular-promise a
new generation of computers capable of solving currently intractable
problems, secure communication, precision metrology, detectors with
unparalleled sensitivity, and an efficient route for synthesizing
new materials. One of the fundamental challenges, however, in
realizing quantum machines is to sustain coherence over a time
interval practical for performing coherent operations or
computation. Until now, boosting coherence has involved hardware
development to minimize coupling to a dissipative environment which
typically transforms a quantum superposition into a classical
state. Recent advances in the development of robust
quantum-noise-limited microwave amplifiers and quantum bits with
lifetimes in excess of 100 microseconds have enabled the use of
feedback to actively suppress decoherence. In particular, we have
been able to tailor the dissipative environment, either via
measurement or excitation pulses, to stabilize quantum superposition
states and coherent oscillations as well as track the evolution of
single and two qubit states. These advances in precision measurement
and control are key for implementing practical quantum circuits for
microwave photonics and interferometry as well as simulations of
exemplar many-body systems such as the Ising chain.