Orchestrated trios: compiling for efficient communication in Quantum programs with 3-Qubit gates

Abstract

Current quantum computers are especially error prone and require high levels of optimization to reduce operation counts and maximize the probability the compiled program will succeed. These computers only support operations decomposed into one-and two-qubit gates and only two-qubit gates between physically connected pairs of qubits. Typical compilers first decompose operations, then route data to connected qubits. We propose a new compiler structure, Orchestrated Trios, that first decomposes to the three-qubit Toffoli, routes the inputs of the higher-level Toffoli operations to groups of nearby qubits, then finishes decomposition to hardware-supported gates.This significantly reduces communication overhead by giving the routing pass access to the higher-level structure of the circuit instead of discarding it. A second benefit is the ability to now select an architecture-tuned Toffoli decomposition such as the 8-CNOT Toffoli for the specific hardware qubits now known after the routing pass. We perform real experiments on IBM Johannesburg showing an average 35% decrease in two-qubit gate count and 23% increase in success rate of a single Toffoli over Qiskit. We additionally compile many near-term benchmark algorithms showing an average 344% increase in (or 4.44x) simulated success rate on the Johannesburg architecture and compare with other architecture types. CCS CONCEPTS• Computer systems organization → Quantum computing; • Software and its engineering → Compilers.

QContext: Context-Aware Decomposition for Quantum Gates

“…Given an input quantum program, QContext first decomposes the gates to 1-qubit gates, 2-qubit gates, and Toffoli gates. Not decomposing the Toffoli gate allows the routing algorithm to capture the program structure and reduce the routing overhead [13]. The compiler performs qubit mapping and routing for the gates.…”

“…We study the basis-gate-level context-aware decomposition for Toffoli gates and the native-gate-level context-aware decomposition for CNOT gates. Our experiments show that QContext reduces the number of gates as compared with the state-of-the-art approach, Orchestrated Trios [13].…”

“…The quantum logic gates in a program typically need to be decomposed to the basis gate set (ISA) in an assembly language. Since the target hardware may have limited connectivity, several recent works [11,13,35,49] propose topologyaware decompositions that minimize the gate cost when mapping to a target hardware topology. However, these decomposition approaches use the same template to decompose the same type of quantum gates.…”

“…Toffoli gate is one of the most commonly used three-qubit gates in quantum information processing. Duckering et al [13] proposed a compiler structure Orchestrated Trios, which efficiently routes and decomposes the Toffoli gates. They observed that it is more efficient to preserve the Toffoli gate during routing instead of routing each individual CNOT gate in the Toffoli gate decomposition.…”

Geyser

“…Circuit composition is essentially the reverse of circuit decomposition. For example, three-qubit gate can be "decomposed" into multiple single-and two-qubit gates that the underlying hardware supports [11,27]. Neutral-atom architectures natively support threequbit gate operations and hence, the circuit composition can reduce a set a of single-and two-qubit operations to an equivalent threequbit operation when it's feasible and does not affect the meaning of the program.…”