In situ measurement and reset of individual qubits with < 1E-3 probability of accidental measurement at the neighbour*

Trapped ions are a versatile platform for quantum information processing. Precise coherent and incoherent/dissipative manipulation of ion-qubits opens new avenues, such as quantum error correction and simulation of measurement driven quantum phases. Recent experiments gained control over coherent operations at the individual qubit level. However, high fidelity incoherent manipulation of individual ion qubits, such as subsystem measurement and reset, is hard. A fundamental limitation is the irreversible decoherence or accidental measurement of the neighbouring ions while addressing the target ion(s). Current approaches to mitigate this issue include 'shuttling' the ions during incoherent operations, which slows the clock speed of a quantum processor and introduces errors. Here, we demonstrate in situ incoherent operations with <1E-3 probability of accidental measurement of the neighbouring qubits. This is enabled by our holographic optical addressing scheme which allows us to achieve ~8E-5 nearest neighbour intensity crosstalk. In situ incoherent operations will increase the processor speed and facilitate exploration of new types of quantum simulations requiring subsystem measurements.