Dispersive Charge and Flux Qubit Readout as a Quantum Measurement Process
نویسندگان
چکیده
We analyze the dispersive readout of superconducting charge and flux qubits as a quantum measurement process. The measurement oscillator frequency is considered much lower than the qubit frequency. This regime is interesting because large detuning allows for strong coupling between the measurement oscillator and the signal transmission line, thus allowing for fast readout. Due to the large detuning we may not use the rotating wave approximation in the oscillator-qubit coupling. Instead we start from an approximation where the qubit follows the oscillator adiabatically, and show that non-adiabatic corrections are small. We find analytic expressions for the measurement time, as well as for the back-action, both while measuring and in the offstate. The quantum efficiency is found to be unity within our approximation, both for charge and flux qubit readout.
منابع مشابه
Time-resolved qubit readout via nonlinear Josephson inductance
We propose a generalization of dispersive qubit readout that provides the time evolution of a flux qubit observable. Our proposal relies on the nonlinear coupling of the qubit to a harmonic oscillator with high frequency, representing a dc superconducting quantum interference device. Information about the qubit dynamics is obtained by recording the oscillator response to resonant driving and su...
متن کاملDispersive measurements of superconducting qubit coherence with a fast latching readout
The “quantronium” is a superconducting qubit consisting of a split Cooper pair box in which a large tunnel junction is inserted. This circuit has a special bias point where the Larmor frequency is, to first order, insensitive to fluctuations in the bias parameters—the charge of the box island and the phase of the large junction. At this optimal working point, the state of the qubit can be deter...
متن کاملNon-Markovian qubit decoherence during dispersive readout
We study qubit decoherence under generalized dispersive readout, i.e., we investigate a qubit coupled to a resonantly driven dissipative harmonic oscillator. We provide a complete picture by allowing for arbitrarily large qubit-oscillator detuning and by considering also a coupling to the square of the oscillator coordinate, which is relevant for flux qubits. Analytical results for the decohere...
متن کاملNondestructive readout for a superconducting flux qubit.
We present a new readout method for a superconducting flux qubit, based on the measurement of the Josephson inductance of a superconducting quantum interference device that is inductively coupled to the qubit. The intrinsic flux detection efficiency and backaction are suitable for a fast and nondestructive determination of the quantum state of the qubit, as needed for readout of multiple qubits...
متن کاملDevelopment of a Silicon Semiconductor Quantum Dot Qubit with Dispersive Microwave Readout
Development of a Silicon Semiconductor Quantum Dot Qubit with Dispersive Microwave Readout
متن کامل