Abstract
AbstractWeak measurement has provided new insight into the nature of quantum measurement, by demonstrating the ability to extract average state information without fully projecting the system. For single-qubit measurements, this partial projection has been demonstrated with violations of the Leggett–Garg inequality. Here we investigate the effects of weak measurement on a maximally entangled Bell state through application of the Hybrid Bell–Leggett–Garg inequality (BLGI) on a linear chain of four transmon qubits. By correlating the results of weak ancilla measurements with subsequent projective readout, we achieve a violation of the BLGI with 27 s.d.s. of certainty.
Highlights
Quantum computing promises greater processing power through the clever application of superposition and entanglement
We demonstrate a continuous and controlled exchange between extracted single-qubit state information and two-qubit entanglement collapse, through the unique framework of the Bell–Leggett–Garg inequality (BLGI). We quantify this effect by correlating variable strength ancilla qubit measurements with subsequent projective readout to collect all the statistics of a Bell inequality experiment[14,15,16,17] in a single quantum circuit
To understand the effect of weak measurement on an entangled state, we combine the spatial correlations of a Bell inequality with the temporal correlations of an Leggett–Garg inequality20 (LGI) to construct a BLGI
Summary
Quantum computing promises greater processing power through the clever application of superposition and entanglement. We quantify this effect by correlating variable strength ancilla qubit measurements with subsequent projective readout to collect all the statistics of a Bell inequality experiment[14,15,16,17] in a single quantum circuit.
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