Operational interpretation and estimation of quantum trace-norm asymmetry based on weak value measurement and some bounds

TL;DR

This paper links the trace-norm asymmetry of quantum states to weak value measurements, providing a practical estimation method and exploring its relation to quantum Fisher information and uncertainty principles.

Contribution

It establishes a laboratory interpretation of trace-norm asymmetry via weak values and proposes a measurement scheme suitable for near-term quantum hardware.

Findings

Trace-norm asymmetry equals the average imaginary part of weak values.

Derived bounds relating trace-norm asymmetry to quantum Fisher information.

Established trade-off relations similar to uncertainty principles.

Abstract

The asymmetry of a quantum state relative to a translational group is a central concept in many areas of quantum science and technology. An important and geometrically intuitive measure of translational asymmetry of a state is given by the trace-norm asymmetry, which is defined as the trace norm of the commutator between the state and the generator of the translation group. While trace-norm asymmetry satisfies all the requirements for a bonafide measure of translational asymmetry of a state within the quantum resource theoretical framework, its meaning in terms of laboratory operations is still missing. Here, we first show that the trace-norm asymmetry is equal to the average absolute imaginary part of the weak value of the generator of the translation group optimized over all possible orthonormal bases of the Hilbert space. Hence, it can be estimated via the measurement of weak value combined with a classical optimization in the fashion of quantum variational circuit which may be implemented using the near-term quantum hardware. We then use the link between the trace-norm asymmetry and the nonreal weak value to derive the relation between the trace-norm asymmetry with other basic concepts in quantum statistics. We further obtain trade-off relations for the trace-norm asymmetry and quantum Fisher information, having analogous forms to the Kennard-Weyl-Robertson uncertainty relation.