QMI Timing Overview

Fig. 104 shows a simplified diagram of the sequence of steps, the dark red set of arrows, to execute a quantum machine instruction (QMI) on a D-Wave system, starting and ending on a user’s client system. Each QMI consists of a single input together with parameters. A QMI is sent across a network to the SAPI server and joins a queue. Each queued QMI is assigned to one of possibly multiple workers, which may run in parallel. A worker prepares the QMI for the quantum processing unit (QPU) and optionally for postprocessing[1], sends the QMI to the QPU queue, receives samples (results) and optionally post-processes them (overlapping in time with QPU execution), and bundles the samples with additional QMI-execution information for return to the client system.

[1]	Postprocessing for D-Wave 2000Q and earlier systems includes optimization and sampling algorithms; on Advantage systems, postprocessing is limited to computing the energies of returned samples. Ocean software provides postprocessing tools, you can use these for Advantage systems.

Fig. 104 Overview of execution of a single QMI, starting from a client system, and distinguishing classical (client, CPU) and quantum (QPU) execution.

The total time for a QMI to pass through the D-Wave system is the service time. The execution time for a QMI as observed by a client includes service time and internet latency. The QPU executes one QMI at a time, during which the QPU is unavailable to any other QMI. This execution time is known as the QMI’s QPU access time.