Quantum State Comparison Amplifier With Feedforward State Correction

Quantum mechanics imposes stringent constraints on the amplification of a quantum signal. Deterministic amplification of an unknown quantum state always implies the addition of a minimal amount of noise(1). Linear and noiseless amplification is allowed in principle provided that it only works probabilistically(28). Here we present a probabilistic amplifier that combines two quantum state comparison amplifiers (SCAMP)(4) together with a feed-forward state correction strategy. Our system outperforms the unambiguous state discrimination (USD)(5) measure-and-resend based amplifier in terms of the success probability-fidelity product and requires a no more complex experimental setting.