Quantitative quantum erasure

Matthias Jakob, János A. Bergou

We present a conditional quantum eraser that erases the a priori knowledge or the predictability of the path a photon takes in a Young-type double-slit experiment with two fluorescent four-level atoms. This erasure violates a recently derived erasure relation which must be satisfied for a conventional, unconditional quantum eraser that aims to find an optimal sorting of the system into subensembles with particularly large fringe visibilities. The conditional quantum eraser employs an interaction-free, partial which-way measurement which not only sorts the system into optimal subsystems with large visibility, but also selects the appropriate subsystem with the maximum possible visibility. We explain how the erasure relation can be violated under these circumstances.

Marcelo Terra Cunha, Sebastio Padua, Stephen Patrick Walborn +1 more

Jitong. Li

Abstract This document explains the source of principles and theoretical basis for the experimental setup described in the Theoretical Prediction and Technical Protocol for a Controlled-Time Quantum Erasure Experiment, the physical logic chain of the experiment, the quantitative veriffcation anchors of the theoretical foundation, as well as a statement against conceptual plagiarism and four judgments on the scientiffc seriousness of the technical protocol. It is ffrst established that: quantum erasure is not an absolutely instantaneous projection, but a physical process in which the information ffeld completes dynamic restructuring within a very limited time window. Based on this, two falsiffable predictions are given: 1) Controlledtime / gradual erasure yields higher interference visibility; 2) Visibility exhibits a nonlinear single-peak distribution with respect to the erasure time window. An original experimental scheme is simultaneously proposed: using a Pockels cell to realize continuous polarization-rotation controlled-time erasure, in contrast with traditional instantaneous ffxed-polarization erasure. Any work that substantively includes any of the core elements (mechanism + prediction + experimental scheme) must cite this document; otherwise, it constitutes academic misconduct.

Stephen Patrick Walborn, Carlos Henrique Monken

Prabha Mandayam, Krishna Jagannathan, Avhishek Chatterjee

We consider a setting where a stream of qubits is processed sequentially. We derive fundamental limits on the rate at which classical information can be transmitted using qubits that decohere as they wait to be processed. Specifically, we model the sequential processing of qubits using a single server queue, and derive expressions for the classical capacity of such a quantum `queue-channel.' Focusing on quantum erasures, we obtain an explicit single-letter capacity formula in terms of the stationary waiting time of qubits in the queue. Our capacity proof also implies that a `classical' coding/decoding strategy is optimal, i.e., an encoder which uses only orthogonal product states, and a decoder which measures in a fixed product basis, are sufficient to achieve the classical capacity of the quantum erasure queue-channel. More broadly, our work begins to quantitatively address the impact of decoherence on the performance limits of quantum information processing systems.

Alexei S. Trifonov, Gunnar G. Bjork, Jonas Söderholm +1 more