Entanglement-Enhanced Lidars for Simultaneous Range and Velocity Measurements

Abstract

Lidar is a well known optical technology for measuring a target's range and radial velocity. We describe two lidar systems that use entanglement between transmitted signals and retained idlers to obtain significant quantum enhancements in simultaneous measurement of these parameters. The first entanglement-enhanced lidar circumvents the Arthurs-Kelly uncertainty relation for simultaneous measurement of range and radial velocity from detection of a single photon returned from the target. This performance presumes there is no extraneous (background) light, but is robust to the roundtrip loss incurred by the signal photons. The second entanglement-enhanced lidar---which requires a lossless, noiseless environment---realizes Heisenberg-limited accuracies for both its range and radial-velocity measurements, i.e., their root-mean-square estimation errors are both proportional to $1/M$ when $M$ signal photons are transmitted. These two lidars derive their entanglement-based enhancements from use of a unitary transformation that takes a signal-idler photon pair with frequencies ${\omega }_S$ and ${\omega }_I$ and converts it to a signal-idler photon pair whose frequencies are $({\omega }_S+{\omega }_I)/2$ and ${\omega }_S-{\omega }_I$. Insight into how this transformation provides its benefits is provided through an analogy to superdense coding.

7 pages, 3 figures

References in corpus (9)

• Quantum Illumination with Gaussian States
• General optimality of the Heisenberg limit for quantum metrology
• Optimum mixed-state discrimination for noisy entanglement-enhanced sensing
• Optimal estimation of joint parameters in phase space
• Storage and retrieval of ultrafast single photons using a room-temperature diamond quantum memory
• Nonlinear interaction between two heralded single photons
• Estimation of unitary quantum operations
• Entanglement is not very useful for estimating multiple phases
• Reduction of Classical Measurement Noise via Quantum-Dense Metrology