Back-action of RC-shunted SQUID on three-junction flux qubit
Abstract
Quantum computation demands a high fidelity readout system that has negligible effect on the qubit during coherent operations. For flux-based quantum computation, the dc SQUID is a natural choice for a readout device; however, to provide good sensitivity without compromising the qubit requires careful design of the damping circuit. We present a SQUID shunted by a resistor and capacitor in series, which provides sufficient resolution for single-shot readout of a qubit while generating a surprisingly small back-action. The shunt suppresses the crossover temperature from thermal activation to quantum tunneling, resulting in narrow switching distributions at low temperatures. At the same time, the capacitor blocks noise currents generated by the resistor, which would otherwise cause the qubit to decohere, from flowing around the loop. We present models of the back-action and thermal activation and quantum tunneling rates. We compare predicted and measured widths of the switching distribution.
- Publication:
-
APS March Meeting Abstracts
- Pub Date:
- March 2004
- Bibcode:
- 2004APS..MARA37002H