Doctor of Philosophy (PhD)


Physics and Astronomy

Document Type



Solid state and condensed matter systems, such as diamond impurities, superconductors, quantum dots, and ion traps, constitute important physical platforms for various applications in quantum information processing (QIP). However, it has consistently been shown that all such modern platforms suffer from non-equilibrium behavior on timescales that are relevant for many important QIP tasks. The causes range from intrinsic non-equilibrium dynamics (e.g. in diamond) to the presence of various impurities with their own internal dynamics (e.g. in superconductors and quantum dots) or variations in the control fields used to stabilize the quantum matter (e.g. in ion traps). When reserving degrees of freedom for QIP in any physical medium, it is therefore important to track and adapt to the non-equilibrium behavior of the rest of relevant degrees of freedom (a.k.a. the environment). In particular, if the environment noise is parameterized by some underlying physical model, then the non-equilibrium behavior will generally yield temporal variations in the noise parameters relevant for QIP. This dissertation proposes a general adaptive refinement to standard QIP (specifically for quantum error correction) by allocating appropriate environment degrees of freedom for use as real-time quantum sensors (a.k.a. spectator systems). This will provide classical side-information about the environment noise parameters in real-time, which is then used to stabilize the performance of the particular QIP task at hand. The main results of this work can be divided into two parts: (1) proposing a realistic physical model for the joint implementation of spectator systems with QIP systems, and (2) studying the fundamental physical limitations of the spectator-based approach, particularly for quantum error correction. This dissertation provides a multi-disciplinary approach to QIP, by attempting to breach the current gap between the mainly mathematical approach to QIP and related physical questions, which ultimately need to be addressed for its realization.



Committee Chair

Lee, Hwang