System characterisation under experimental constraints

  • Kaila Hall

Student thesis: Doctoral Thesis


Physically realising quantum computation is our long term goal. Currently characterising and verifying quantum states is a hard problem. Verification is necessary in order to understand and control quantum systems. There are also issues in the physical realisation of these systems, the apparatus used does not match the quantum scale and so produces errors in the measurements. There are many different candidates for physically realising quantum computation, we consider measurement based quantum computation using cluster state systems. We explore the different ways of verifying these systems in the presence of various experimental imperfections and non-idealities. We present a scheme to reduce the cross-talk found when verifying the state through stabilizer operator measurements. The cross-talk comes from physical constraints on the measurement apparatus. Our scheme reduces the cross-talk to almost 50% of the original value. We consider square, triangular and hexagonal connectivity lattices. We also use the Clauser-Horne-Shimony-Holt (CHSH) inequality as a way to verify atoms trapped in optical lattices through its entanglement. Imperfections arise in this system through finite entropy in the creation process that leads to vacant lattice sites. By optimising the conventional measurement settings we improve the tolerance of the system to incomplete measurement and vacancies. We find violations of the CHSH inequality for very large vacancy rates. We analyse further errors in the detectors and calculate the tolerance of the system in these cases. We study the effects of superselection rules and their connection to the single particle entanglement question. We review a system presented by Paterek et al. and verify it again using the CHSH inequality. We introduce errors into the measurement process. By optimising the measurement settings we increase the tolerance of the system for four different error models.We also explore how non-ideal state preparation affects the detectable violations.
Date of Award1 Apr 2015
Awarding Institution
  • University Of Strathclyde
SponsorsEPSRC (Engineering and Physical Sciences Research Council)
SupervisorDaniel Oi (Supervisor) & John Jeffers (Supervisor)

Cite this