Abstract
Accurate time-delay measurement is at the core of many modern technologies. We present a temporal-mode demultiplexing scheme that achieves the ultimate quantum precision for the simultaneous estimation of the temporal centroid, the time offset, and the relative intensities of an incoherent mixture of ultrashort pulses at the single-photon level. We experimentally resolve temporal separations 10 times smaller than the pulse duration, as well as imbalanced intensities differing by a factor of . This represents an improvement of more than an order of magnitude over the best standard methods based on intensity detection.
- Received 3 September 2020
- Accepted 12 November 2020
DOI:https://doi.org/10.1103/PRXQuantum.2.010301
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)
Viewpoint
Getting a Handle on Timing
Published 4 January 2021
Ideas from superresolution imaging inspire a way to measure time intervals with unprecedented precision—an ability that could enhance our understanding of ultrafast processes.
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Popular Summary
In any lab, researchers perform measurements and collect data in order to learn the properties of their system. Oftentimes, they are estimating a certain parameter, such as length, weight, or position. Most parameters have natural measurement tools to use, such as the light intensity on a camera to measure position. But are these tools the best possible ones? Can we estimate these parameters with more precision and less data using different tools?
In this work, a set of measurements is described that can be used to simultaneously measure multiple temporal properties of pulses of light. These measurements are found by analyzing the problem using the tools of quantum information, which can optimize over all possible measurements allowed in quantum mechanics. Rather than measuring intensity alone, these methods detect coherent pulse shapes called temporal modes, which provide both intensity and phase information. The researchers used nonlinear optics in optical chips called waveguides to build these measurements, constructing a quantum pulse gate that only allows photons through if they match a specific pulse shape. By applying these methods to dim laser pulses, the researchers showed an order-of-magnitude improvement in the per-photon estimation precision over the best theoretical timing measurement possible that uses intensity only.
The tools developed and demonstrated in this work can be applied in astronomy, ranging, clock synchronization, and biological imaging. They may also be adapted to other types of measurement using light, such as optical frequency and spatial positioning.