Quantum amplification and purification of noisy coherent states

Abstract

Quantum-limited amplifiers increase the amplitude of quantum signals at the price of introducing additional noise. Quantum purification protocols operate in the reverse way, by reducing the noise while attenuating the signal. Here we investigate a scenario that interpolates between these two extremes. We search for the optimal physical process that generates $M$ approximate copies of pure and amplified coherent state, starting from $N$ copies of a noisy coherent state with Gaussian modulation. We prove that the optimal deterministic processes are always Gaussian, whereas non-Gaussianity powers up probabilistic advantages in suitable parameter regimes. The optimal processes are experimentally feasible, both in the deterministic and in the probabilistic scenario. In view of this fact, we provide benchmarks that can be used to certify the experimental demonstration of the quantum-enhanced amplification and purification of coherent states.

10 pages

References in corpus (14)

• Experimental study on Gaussian-modulated coherent states quantum key distribution over standard telecom fiber
• The optimal cloning of quantum coherent states is non-Gaussian
• Quantum limits on phase-preserving linear amplifiers
• Security of coherent state quantum cryptography in the presence of Gaussian noise
• Squeezing the limit: Quantum benchmarks for the teleportation and storage of squeezed states
• Quantum Benchmark for Teleportation and Storage of Squeezed States
• Phase-Covariant Quantum Benchmarks
• Fidelity criterion for quantum-domain transmission and storage of coherent states beyond unit-gain constraint
• Optimal probabilistic estimation of quantum states
• Fundamental quantum limits for practical devices
• Simple proof of the quantum benchmark fidelity for continuous-variable quantum devices
• Models of reduced-noise, probabilistic linear amplifiers
• Superbroadcasting of conjugate quantum variables
• Quantum Benchmark via an Uncertainty Product of Canonical Variables

Cited by in corpus (7)

• Noiseless attenuation using an optical parametric amplifier
• Efficient verification of continuous-variable quantum states and devices without assuming identical and independent operations
• Reduced decoherence using squeezing, amplification, and anti-squeezing
• Test one to test many: a unified approach to quantum benchmarks
• Effect of incoherent pump on two-mode entanglement in optical parametric generation
• Indirect Measurement for Optimal Quantum Communication Enhanced by Binary Non-standard Coherent States
• Sensitivity of Measurement-Based Purification Processes to Inner Interactions