Ancilla-free implementation of POVM measurements for near-term quantum algorithms

Abstract

Positive Operator-Valued Measures (POVMs) describe a class of generalized quantum measurements offering conceptual and operational advantages over the usual computational basis readout. In particular, Informationally Complete (IC) POVMs can be employed for efficient partial state tomography and to measure observable expectation values with performances that surpass those of standard operator averaging methods, as recently demonstrated by García-Pérez et al. [1]. In this work, we propose an ancilla-free scheme for the practical implementation of POVM readout in IBM superconducting processors. This method alleviates the main drawback of traditional IC-POVM measurement schemes, which typically require the use of accessory qubit resources and may thus be demanding in terms of device size and connectivity. We present experimental results for proof-of-principle applications to paradigmatic quantum information tasks, along with systematic studies of control pulse sequences and hardware requirements. [1] G. García-Pérez et al., arXiv:2104.00569 (to appear in PRX Quantum)