Abstract
Noise can be considered the natural enemy of quantum information. An often implied benefit of high-dimensional entanglement is its increased resilience to noise. However, manifesting this potential in an experimentally meaningful fashion is challenging and has never been done before. In infinite dimensional spaces, discretization is inevitable and renders the effective dimension of quantum states a tunable parameter. Owing to advances in experimental techniques and theoretical tools, we demonstrate an increased resistance to noise by identifying two pathways to exploit high-dimensional entangled states. Our study is based on two separate experiments utilizing canonical spatiotemporal properties of entangled photon pairs. Following these different pathways to noise resilience, we are able to certify entanglement in the photonic orbital-angular-momentum and energy-time degrees of freedom up to noise conditions corresponding to a noise fraction of 72% and 92%, respectively. Our work paves the way toward practical quantum communication systems that are able to surpass current noise and distance limitations, while not compromising on potential device independence.
- Received 1 August 2019
- Revised 11 October 2019
DOI:https://doi.org/10.1103/PhysRevX.9.041042
Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.
Published by the American Physical Society
Physics Subject Headings (PhySH)
Synopsis
Entanglement in Broad Daylight
Published 26 November 2019
Photons entangled in high dimensions are more resilient to noise, making them ideal for quantum communication applications.
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Popular Summary
Distributing entangled photons between distant communication parties is essential for most tasks in quantum communication. Unfortunately, many photons are disturbed, lost, or replaced by ambient photons during transmission over long distances and through realistic environments. At some point, the resulting noise will dominate the shared quantum state, and entanglement can no longer be extracted. We demonstrate how to recover entanglement by resorting to higher dimensions of the quantum state and give experimental proof of noise resistance with entangled photon pairs.
The physical properties of a photon, such as frequency or position, are continuous in nature. Encoding information in photons, therefore, necessitates a choice of the discretization of these properties and the number of modes considered: Discretizing with higher resolution leads to dilution of the noise, while increasing the number of modes enables more measurements. We demonstrate these pathways to noise resilience in two experiments that employ entanglement in the creation time and momentum of photon pairs.
Most quantum communication protocols rely on the distribution of quantum bits (qubits), or two-level systems. Since it is now evident that high-dimensional entanglement enables quantum communication beyond the noise limitations of qubits, the next goal is to develop protocols that make use of high-dimensional states.