Anticipative measurements in hybrid quantum-classical computation
Before the availability of large scale fault-tolerant quantum devices, one has to find ways to make the most of current noisy intermediate-scale quantum devices. One possibility is to seek smaller repetitive hybrid quantum-classical tasks with higher fidelity, rather than directly pursuing large complex tasks. We present an approach in this direction where the quantum computation is supplemented by a classical result. While the presence of the supplementary classical information helps alone, taking advantage of its anticipation also leads to a new type of quantum measurements, which we call anticipative. Anticipative quantum measurements lead to improved success rate over cases where we would use quantum measurements optimized without assuming the later arriving supplementing information. Importantly, in an anticipative quantum measurement the combination of the results from classical and quantum computations happens only in the end, without the need for feedback from the one to the other computation, a feature which hence allows for running both computations in parallel. We demonstrate the method with an experiment using an IBMQ device and show that it leads to an improved success rate even in a real noisy setting.