JQI

Abstract: Irreversible quantum computation requires thermodynamic work. In principle, one can often evade work costs by implementing reversible transformations. In practice, complexity---the difficulty of realizing a quantum process---poses an obstacle: a realistic agent can perform only a limited number of gates and so not every reversible transformation. Hence an agent, if unable to complete a task unitarily, may expend work on an irreversible process, such as erasure, to finish the job.

Dissertation Committee Chair: Mohammad Hafezi

Committee: 

Jay Deep Sau

You Zhou

Aaron Sternbach

Ian B. Spielman

Christopher Jarzynski (Dean’s representative)

Dissertation Committee Chair: Christopher J. Lobb

Committee:

Jacob M. Taylor

Victor M. Galitski

Saikat Guha

Alicia J. Kollar

Abstract: There is a deep connection between quantum error correction and phases of matter for spatially local codes in finite dimensions.  I will show how this analogy extends to more general settings: quantum codes with check soundness are absolutely stable phases of matter.  These codes include constant-rate quantum low-density parity-check codes, which shows that the third law of thermodynamics is false: there exist absolutely stable phases of matter with constant entropy density at zero temperature.

Abstract: Inspired by natural cooling processes, dissipation has become a promising approach for preparing low-energy states of quantum systems. However, the potential of dissipative protocols remains unclear beyond certain commuting Hamiltonians.

Abstract: Experimental control over the strength and angular dependence of interactions between atoms is a key capability for advancing quantum technologies. Here, we use microwave dressing to manipulate and enhance Rydberg-Rydberg interactions in an atomic ensemble. By resonantly coupling opposite parity Rydberg states, we create eigenstates with first-order dipole-dipole interactions. We study the modification of the interactions by measuring the statistics of the light retrieved from the ensemble.

Dissertation Committee Chair: Maissam Barkeshli

Committee: 

Andrey Gromov (advisor)

Victor Albert

Tom Goldstein

Christopher Jarzynski (Dean’s representative)

Optomechanical detectors offer a highly sensitive method for measuring weak forces. By optically trapping these systems in high vacuum, one can drastically reduce environmental noise and achieve exquisite control over the detector’s center-of-mass motion, rotational degrees of freedom, and physical characteristics such as charge states. This level of isolation enables the detector’s noise to reach the quantum measurement regime, where the dominant noise source is the measurement process itself.