Experimental study of ballistic fluxon detectors for superconducting qubits

• Applicant: Professor Alexey V. Ustinov, Ph.D.
• Subject Area: Experimental Condensed Matter Physics
• Term: from 2007 to 2011
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 49045566

We would like to design, fabricate and experimentally investigate new type of detectors for very fast and weakly perturbing readout of superconducting qubits. The detection principle is based on measuring the delay time of a ballistic fluxon moving in a Josephson transmission line when passing by a qubit. Due to the pinning potential induced by the localized magnetic flux of the qubit, the fluxon propagation delay depends on the state of the qubit. The expected advantage of ballistic fluxon detectors over existing readout techniques used for superconducting qubits are low dissipated power, high time resolution and small back action on the qubit. We will perform fluxon delay measurements by (i) detecting the fluxon oscillation frequency shift, (ii) measuring the output phase shift of the frequency-locked fluxon injection and (iii) directly by using a fluxon interferometer. Ballistic fluxon detectors should be suitable for implementation of non-destructive measurement schemes with superconducting qubits, including quantum non-demolition readout and feedback control schemes.

• DFG Programme: Research Grants