Abstract
Measurements leading to the collapse of states and the non-local quantum correlations are the key to all applications of quantum mechanics as well as in the studies of quantum foundation. The former is crucial for quantum parameter estimation, which is greatly affected by the physical environment and the measurement scheme itself. Its quantification is necessary to find efficient measurement schemes and circumvent the non-desirable environmental effects. This has led to the intense investigation of quantum metrology, extending the Cramér–Rao bound to the quantum domain through quantum Fisher information. Among all quantum states, the separable ones have the least quantumness; being devoid of the fragile non-local correlations, the component states remain unaffected in local operations performed by any of the parties. Therefore, using these states for the remote design of quantum states with high quantum Fisher information can have diverse applications in quantum information processing; accurate parameter estimation being a prominent example, as the quantum information extraction solely depends on it. Here, we demonstrate that these separable states with the least quantumness can be made extremely useful in parameter estimation tasks, and further show even in the case of the shared channel inflicted with the amplitude damping noise and phase flip noise, there is a gain in Quantum Fisher information (QFI). We subsequently pointed out that the symmetric W states, incapable of perfectly teleporting an unknown quantum state, are highly effective for remotely designing quantum states with high quantum Fisher information.
Highlights
The precise measurement of a parameter is one of the most crucial tasks in scientific researches
We have shown in this work that with a shared entangled state between two spatially separated parties Alice and Bob, Alice can create a state at Bob’s end that attains higher quantum Fisher information using only local operations and classical communication, starting with an initial unknown 2-qubit mixed state
Quantum Fisher information (QFI) depends on the channel and Alice’s choice measurement bases, while it is independent of the initial state parameter
Summary
The precise measurement of a parameter is one of the most crucial tasks in scientific researches. Quantum protocols like teleportation [16,17,18,19], and remote state preparation [20,21,22,23,24] make use of entangled states shared between two spatially separated parties such as a channel, and perform LOCC to achieve their goal. We provide a quantum protocol, where two spatially separated parties, Alice and Bob, share an entangled quantum state as ’channel’, and Alice prepares a state with higher quantum Fisher information at Bob’s end starting with an unknown 2-qubit single parameter Werner state [25]. Our results state that for the separable initial states taken by Alice, the average QFI of Bob’s final state crosses the separable limit, making them useful in quantum metrology.
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