Quantum Time-evolution in Qubit Readout Process with a Josephson Bifurcation Amplifier - Condensed Matter > Mesoscale and Nanoscale PhysicsReport as inadecuate




Quantum Time-evolution in Qubit Readout Process with a Josephson Bifurcation Amplifier - Condensed Matter > Mesoscale and Nanoscale Physics - Download this document for free, or read online. Document in PDF available to download.

Abstract: We analyzed the Josephson bifurcation amplifier JBA readout process of asuperconducting qubit quantum mechanically. This was achieved by employingnumerical analyses of the dynamics of the density operator of a drivennonlinear oscillator and a qubit coupled system during the measurement process.In purely quantum cases, the wavefunction of the JBA is trapped in aquasienergy-state, and bifurcation is impossible. Introducing decoherenceenables us to reproduce the bifurcation with a finite hysteresis. Moreover, wediscuss in detail the dynamics involved when a qubit is initially in asuperposition state. We have observed the qubit-probe JBA entangled state andit is divided into two separable states at the moment of the JBA transitionbegins. This corresponds to -projection-. To readout the measurement result,however, we must wait until the two JBA states are macroscopically wellseparated. The waiting time is determined by the strength of the decoherence inthe JBA.



Author: Hayato Nakano, Shiro Saito, Kouichi Semba, Hideaki Takayanagi

Source: https://arxiv.org/



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