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Indefinite Time Directed Quantum Metrology by Agrawal, Gaurang; Halder, Pritam; De, Aditi Sen is a scholarly article available to read on EtoBox.

What is Indefinite Time Directed Quantum Metrology about?

We explore the performance of the metrology scheme by employing a quantum time flip during encoding, a specific case of processes with indefinite time direction, which we refer to as indefinite time directed metrology (ITDM). In the case of single parameter estimation of a unitary, we demonstrate that our protocol can achieve Heisenberg scaling (1/N) with product probe states, surpassing the standard quantum limit (1/\sqrt{N}), where N is the number of particles in the probe. We establish this by computing the quantum Fisher information (QFI) which is a lower bound on the root mean square error occurred during parameter estimation. Although we analytically prove the optimality of the symmetric product probe state in ITDM, entangled probe states produce a higher QFI than optimal product probes without enhancing scaling, highlighting the non-essentiality of entanglement. For phase estimation, we propose a single-qubit measurement on the control qubit that accomplishes near-optimal Fisher information and eventually reaches Heisenberg scaling. Our findings reveal the best orientation of product probe states in every pertinent situation, emphasizing its independence from the parameter t

Author

Agrawal, Gaurang; Halder, Pritam; De, Aditi Sen

Published

2025

Language

EN