Quantum Optimal control with superconducting qubits for quantum information processing.
Lead Research Organisation:
University of Surrey
Department Name: ATI Physics
Abstract
In the 80's a new idea in computing was proposed: a universal quantum computer. This new computer would function differently to how a classical computer works, and in fact the new paradigm could outperform the classical computer at different tasks.
The information on a quantum computer is continuous while on a classical computer it is discrete and this introduces a whole range of problems that did not exist previously.
Qubits are the smallest units of information for a quantum computer, analogous to the bit which exists as either 0 or 1 in a classical computer. Experimentally, qubits have many implementation that can be vastly different, the one that my research is most focussed toward is the Josephon junction operated in the Transmon regime, a qubit that is not sensitive to charge noise.
In order to get any sort of useful output from these qubits some operations need to be carried out. Despite these operations not being achieved perfectly there exists an error rate for which computation will be feasible with some error correcting scheme, using some redundancy in the qubit. This repetition of information can increase the number of qubits by a factor greater than a thousand! By obtaining extremely high fidelity, a measure of the reliability of the execution of said operation, this overhead can be reduced.
The way these reliable operations are achieved is by using microwave pulses. However, in the presence of fluctuations in the parameters of the qubit or when there is noise, the value for the fidelity drops significantly. A strategy needs to be found to fight those undesirable effects: I use sequential convex programming, a gradient search optimisation method, to find pulses that will be robust to these fluctuations and noise. Due to the sensitivity to the initial condition of the optimisation a large number of starting points need to be used to explore the fidelity landscape this requires code that can be run on multiple computers at once.
In the future, I would like to look at different systems.
The information on a quantum computer is continuous while on a classical computer it is discrete and this introduces a whole range of problems that did not exist previously.
Qubits are the smallest units of information for a quantum computer, analogous to the bit which exists as either 0 or 1 in a classical computer. Experimentally, qubits have many implementation that can be vastly different, the one that my research is most focussed toward is the Josephon junction operated in the Transmon regime, a qubit that is not sensitive to charge noise.
In order to get any sort of useful output from these qubits some operations need to be carried out. Despite these operations not being achieved perfectly there exists an error rate for which computation will be feasible with some error correcting scheme, using some redundancy in the qubit. This repetition of information can increase the number of qubits by a factor greater than a thousand! By obtaining extremely high fidelity, a measure of the reliability of the execution of said operation, this overhead can be reduced.
The way these reliable operations are achieved is by using microwave pulses. However, in the presence of fluctuations in the parameters of the qubit or when there is noise, the value for the fidelity drops significantly. A strategy needs to be found to fight those undesirable effects: I use sequential convex programming, a gradient search optimisation method, to find pulses that will be robust to these fluctuations and noise. Due to the sensitivity to the initial condition of the optimisation a large number of starting points need to be used to explore the fidelity landscape this requires code that can be run on multiple computers at once.
In the future, I would like to look at different systems.
Organisations
Studentship Projects
| Project Reference | Relationship | Related To | Start | End | Student Name |
|---|---|---|---|---|---|
| EP/N509772/1 | 01/10/2016 | 30/09/2021 | |||
| 1911135 | Studentship | EP/N509772/1 | 03/07/2017 | 31/12/2020 | Max Cykiert |