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.
Diagram showing an overview of the execution of a QMI on the system, highlighting QPU access and service time.

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.