# Pulse level description of quantum circuits

The aim of this proposal is to enhance QuTiP quantum-circuit compilation features with regard to quantum information processing. While QuTiP core modules deal with dynamics simulation, there is also a module for quantum circuits simulation. The two subsequent Google Summer of Code projects, in 2019 and 2020, enhanced them in capabilities and features, allowing the simulation both at the level of gates and at the level of time evolution. To connect them, a compiler is implemented to compile quantum gates into the Hamiltonian model. We would like to further enhance this feature in QuTiP and the connection with other libraries.

## Expected outcomes

- APIs to import and export pulses to other libraries. Quantum compiler is a current research topic in quantum engineering. Although QuTiP has a simple compiler, many may want to try their own compiler which is more compatible with their quantum device. Allowing importation and exportation of control pulses will make this much easier. This will include a study of existing libraries, such as qiskit.pulse and OpenPulse [1], comparing them with qutip.qip.pulse module and building a more general and comprehensive description of the pulse.

- More examples of quantum system in the qutip.qip.device module. The circuit simulation and compilation depend strongly on the physical system. At the moment, we have two models: spin chain and cavity QED. We would like to include some other commonly used planform such as Superconducting system [2], Ion trap system [3] or silicon system. Each model will need a new set of control Hamiltonian and a compiler that finds the control pulse of a quantum gate. More involved noise models can also be added based on the physical system. This part is going to involve some physics and study of commonly used hardware platforms. The related code can be found in qutip.qip.device and qutip.qip.compiler.

## Skills

- Git, Python and familiarity with the Python scientific computing stack

- quantum information processing and quantum computing (quantum circuit formalism)

## Difficulty

- Medium

## Mentors

- Boxi Li (etamin1201@gmail.com) [QuTiP GSoC 2019 graduate]

- Nathan Shammah (nathan.shammah@gmail.com)

- Alex Pitchford (alex.pitchford@gmail.com)

## References

[1]

McKay D C, Alexander T, Bello L, et al. Qiskit backend specifications for openqasm and openpulse experiments[J]. arXiv preprint arXiv:1809.03452, 2018.

[2]

Häffner H, Roos C F, Blatt R, Quantum computing with trapped ions, Physics reports, 2008, 469(4): 155-203.

[3]

Krantz P, Kjaergaard M, Yan F, et al. A quantum engineer’s guide to superconducting qubits, Applied Physics Reviews, 2019, 6(2): 021318.