VTDE
Variational Trace Distance Estimation
**Variational Trace Distance Estimation**, or **VTDE**, is a variational algorithm for trace norm estimation that only involves one ancillary qubit. Notably, the cost function in VTDE gathers information from a single-qubit observable and thus could avoid the barren plateau issue with logarithmic depth parameterized circuits.
Variational Quantum Algorithms for Trace Distance and Fidelity Estimation
https://paperswithcode.com/paper/variational-quantum-algorithms-for-trace
Variational Quantum Algorithms for Trace Distance and Fidelity Estimation