Noise and the Single Qubit

Kristian Rabenstein, Viktor A. Sverdlov, D. V. Averin

Fu‐Guo Deng, Xihan Li, Hong-Yu Zhou

We propose a passively self-error-rejecting single-qubit transmission scheme for an arbitrary polarization state of a single qubit over a collective-noise channel, without resorting to additional qubits and entanglement. By splitting a single qubit into some wavepackets with some Mach-Zehnder interferometers, we can obtain an uncorrupted state with a success probability approaching 100% via postselection in different time bins, independent of the parameters of collective noise. It is simpler and more flexible than the schemes utilizing decoherence-free subspace and those with additional qubits. One can directly apply this scheme to almost all quantum communication protocols based on single photons or entangled photon systems against a collective noise.

François Chapeau-Blondeau

Juan S. Rojas-Arias, Peter Stano, Yi-Hsien Wu +3 more

We introduce Single-Shot Cross-Spectroscopy (SSCS), a method for extracting the auto- and cross-power spectral densities of dephasing noise in a qubit pair. The method uses straightforward input, namely, single-shot readouts from single-qubit Ramsey-type experiments, without requiring the reconstruction of qubit energy fluctuations from repeated measurements, and is resilient against errors in state preparation and measurement. We apply it to experimental data from a semiconductor spin-qubit device and obtain noise spectra over five orders of magnitude in frequency (5 mHz–500 Hz). Compared to other techniques, for spin qubits, SSCS enables access to noise correlations in the previously inaccessible intermediate-frequency range (1–500 Hz), and can be further extended with faster readout. The method is directly applicable to other qubit platforms, and the upper frequency it can probe is set by the repetition rate of a single-qubit preparation and measurement.

Ping Zhou, Li Lv, Liang Ming He

The effect of noise on the transmission of quantum state has attached much interest recently. Here we investigate the effect of different types of quantum noise on deterministic exact remote preparation of an arbitrary single-qubit state. Four types of noise which usually encountered in application of quantum remote state preparation, including bit-flipping, phase-flipping, depolarizing and amplitude damping, are considered. The average fidelities of remote state preparation for any combinations of noise are calculated. It is shown that more fidelity can be achieved via less entanglement in single-qubit remote preparation when part or all of the entangled qubits are subjected to amplitude damping noise. It is shown that in several situations more noise may leading to more fidelity in remote state preparation. Moreover, we discuss the effect of noise on probabilistic remote state preparation.

Daniele Cuomo