Defence of dissertation in the field of engineering physics, Sergey Danilin, M.Sc.

2018-05-18 12:00:00 2018-05-18 23:59:06 Europe/Helsinki Defence of dissertation in the field of engineering physics, Sergey Danilin, M.Sc. For what can superconducting artificial atoms be used? http://physics.aalto.fi/en/midcom-permalink-1e83d55b3d5a91e3d5511e88bf0d59007e7938c938c Otakaari 4, 02150, Espoo

For what can superconducting artificial atoms be used?

18.05.2018 / 12:00
Aalto University, lecture hall K216, Otakaari 4, 02150, Espoo, FI

Sergey Danilin, M.Sc., will defend the dissertation "Experiments with a transmon artificial atom – state manipulation and detection of magnetic fields" on 18 May 2018 at 12 noon at the Aalto University School of Science. Superconducting artificial atoms are the central elements for the quantum computation based on superconducting quantum circuits. They also find applications as the tools for the tasks of quantum metrology.

Practical work on constructing quantum computers has started already a few decades ago. The operation principles of a quantum computer rely on the laws of quantum mechanics instead of classical physics. The same as a register of bits of a classical computer a quantum computer should have a quantum register comprising quantum objects (atoms, photons, nuclei, superconducting artificial atoms). The replacement of a computer hardware from classical to quantum one endows a quantum computer with an increased computational power. Among other physical platforms, uperconducting quantum circuits seem to be very attractive to realize a quantum computer. Superconducting artificial atoms of "transmon" type
can play a role of the elements composing the quantum register. The circuits comprising the superconducting artificial atoms were studied in the dissertation.

To build a quantum computer a few requirements have to be fulfilled (they are known as DiVincenzo's criteria). The dissertation addresses two of them. Firstly, the control microwave pulses useful for the initialization of a quantum register were studied. The advantages of adiabatic (slow) pulses and the methods to shorten their duration without losing the advantages were demonstrated experimentally. Secondly, the operations done on the elements of a quantum register are called gates, they are required for the operation of a quantum computer. The gates based on geometric phases were implemented on the circuit studied in the dissertation.

Finally, in addition to quantum computational applications the same circuit was used as a magnetic field or flux sensor. The sensitivity of the sensor is increased using two modified phase estimation algorithms. The method has a huge potential in the improvement of the sensor sensitivity to the level competing or even exceeding the sensitivity of the best up to date magnetic flux sensors. The required improvements are possible to implement with nowadays technological advances.

Dissertation press release (pdf)

Opponent: Associate Professor Gary Steele, Delft University of Technology, The Netherlands

Custos: Professor Jukka Pekola, Aalto University School of Science, Department of Applied Physics 

Electronic dissertation: http://urn.fi/URN:ISBN:978-952-60-7956-1