Direct evaluation of measurement uncertainties by feedback compensation of decoherence

用于抑制冷原子量子存储器塞曼退相干的空间前馈矩阵解耦与滞环PI调节三轴主动磁补偿

Three-axis Active Magnetic Compensation with Spatial Feedforward Matrix Decoupling and Hysteresis PI Regulation for Suppressing Zeeman Decoherence of Cold Atom Quantum Memories

本文提出一种空间前馈矩阵解耦与滞环PI调节的三轴主动磁补偿架构，通过硬件、算法与控制方法优化，显著提升冷原子量子存储器零磁场区域的均匀性与长期稳定性，实现了高精度的磁场抑制效果。

Prediction and real-time compensation of qubit decoherence via machine-learning

The wide-ranging adoption of quantum technologies requires practical, high-performance advances in our ability to maintain quantum coherence while facing the challenge of state collapse under measurement. Here we use techniques from control theory and machine learning to predict the future evolution of a qubit's state; we deploy this information to suppress stochastic, semiclassical decoherence, even when access to measurements is limited. First, we implement a time-division-multiplexed approach, interleaving measurement periods with periods of unsupervised but stabilised operation during whic…

Compensation of decoherence from telegraph noise by means of bang-bang control

With the growing efforts in isolating solid-state qubits from external decoherence sources, the origins of noise inherent to the material start to play a relevant role. One representative example are charged impurities in the device material or substrate, which typically produce telegraph noise and can hence be modelled as bistable fluctuators. In order to demonstrate the possibility of the active suppression of the disturbance from a {\em single} fluctuator, we theoretically implement an elementary bang-bang control protocol. We numerically simulate the random walk of the qubit state on the B…

Quantum Uncertainties in the Schmidt Basis Given by Decoherence

A common misconception is that decoherence gives the eigenstates that we observe to be fairly definite about a subsystem (e.g., approximate eigenstates of position) as the elements of the Schmidt basis in which the density matrix of the subsystem is diagonal. Here I show that in simple examples of linear systems with gaussian states, the Schmidt basis states have as much mean uncertainty about position as the full density matrix with its combination of different possibilities.

Intrinsic time-uncertainties and decoherence: comparison of 4 models

Four models of energy decoherence are discussed from the common perspective of intrinsic time-uncertainty. The four authors -- Milburn, Adler, Penrose, and myself -- have four different approaches. The present work concentrates on their common divisors at the level of the proposed equations rather than at the level of the interpretations. General relationships between time-uncertainty and energy-decoherence are presented in both global and local sense. Global and local master equations are derived. (The local concept is favored.)

Microscopic and Macroscopic Effects in the Decoherence of Neutrino Oscillations

We present a generic structure (the layer structure) for decoherence effects in neutrino oscillations, which includes decoherence from quantum mechanical and classical uncertainties. The calculation is done by combining the concept of open quantum system and quantum field theory, forming a structure composed of phase spaces from microscopic to macroscopic level. Having information loss at different levels, quantum mechanical uncertainties parameterize decoherence by an intrinsic mass eigenstate separation effect, while decoherence for classical uncertainties is typically dominated by a statist…