JoRGS: Joint Rotation Gate Synthesis

Introduction

JoRGS is a synthesis tool for quantum rotation gates implemented in C/C++. Given a circuit containing commuting rotation gates, JoRGS helps to synthesize it into the Clifford+T gate set with minimal T-count.

Build

To build the binary file JoRGS, just use the following:

make

Execution

The circuit format being simulated is OpenQASM used by IBM's Qiskit, and the gate set supported in this simulator now contains Rotation-X (rx), Rotation-Y (ry), Rotation-Z (rz), Rotation-XX (rxx), Rotation-YY (ryy), Rotation-ZZ (rzz), Phase (p), and Controlled-phase (cp). One can find example circuits in the examples folder.

The help message states the details:

$ ./JoRGS --help
Options:
  --help                produce help message
  --in arg              qasm file string for synthesis
  --out arg             qasm file string after synthesis
  --prec arg (=30)      precision in bits (default: 30)
  --cost arg (=1000)    T-count of applying an independent single-gate rotation. Set it to a large number to disable applying single-gate rotations (default: 1000)
  --same                use Fourier state transformation for the same-angle special case

For example, the following command synthesizes example/vqe_layer.qasm, which is a layer in a VQE circuit.

./JoRGS --in examples/vqe_layer.qasm --out out.qasm --prec 30

Then the synthesized circuit is produced in out.qasm. In the output circuit, two ancilla quantum registers are used. It is assumed that the "add" register is initialized as 0, and the "frs" register has been initialized as the Fourier state. Moreover, the method in [C. Gidney, 2018] can be applied for canceling the Toffoli gates, which is used to calculate the T-count, but we keep the original circuit for clarity.

For the case that all rotation gates have the same rotation angles, the --same argument can be applied.
For example, the following command synthesizes example/qaoa_layer.qasm, which is a layer in a QAOA circuit. The --cost 44 parameter specifies the T-count of applying each single-gate rotation with the RUS method used in the Fourier state transform.

./JoRGS --in examples/qaoa_layer.qasm --out out.qasm --prec 30 --cost 44 --same

Note that we do not consider the T-count of the inverse Fourier state transform, as stated in the paper, but we keep it in the output circuit for clarity.