Making conventional computers pretend to be quantum computers

 

Emulation: Making conventional computers pretend to be quantum computers

The ideal way to test out an idea for a quantum algorithm, or an error mitigation technique, is of course to try it on a real quantum system. As more and more prototype quantum devices are put online, this becomes a real possibility. But in the current environment, the devices available are limited in scale, oversubscribed, and may suffer very severe levels of noise. Moreover, a given quantum device will have specific noise and connectivity properties that are ‘baked in’ whereas an algorithm designer may wonder how their idea will perform on systems that don’t yet even exist. For these reasons it is vital to have the power of emulation.
 
In the Hub a family of emulators called QuEST (Quantum Exact Simulation Toolkit) has been developed. It is a C and C++ based simulation framework which supports a rich set of operations like Pauli gadgets, multi-qubit general unitaries, density matrices, and general Kraus maps. QuESTlink integrates these in Mathematica and pyQuEST gives Python programmers access to this resource. These emulators can run on local (e.g., laptop), multi-core, GPU, and distributed systems seamlessly. QuESTlink can even use remote hardware to perform simulations, with the results accessible within Mathematica. 

QuEST can run on local (e.g., laptop), multi-core, GPU, and distributed systems seamlessly. QuESTlink can even use remote hardware to perform simulations

 
To include noise the Virtual Quantum Device (VQD) platform was introduced [1]. This is a system based on the QuEST quantum emulator. Using VQDs, non-expert users can emulate specific quantum computers with detailed error models, bespoke gate sets and connectivity. Five families of VQDs corresponding to trapped ions, nitrogen- vacancy centres, neutral atom arrays, silicon quantum dot spins, and superconducting devices were created and explored, with close collaboration across our hardware work packages helping to enable this. The VQD platform offers researchers the ability to rapidly explore algorithms and protocols in a realistic setting; meanwhile, hardware experts can create their own VQDs to compare with their experiments.

More information on QuEST can be found at: https://quest.qtechtheory.org

 
[1] The Virtual Quantum Device (VQD): A tool for detailed emulation of quantum computers. C. Gustiani, T. Jones and S. Benjamin, arXiv:2306.07342.