Super-resolution localization and readout of individual solid-state qubits

Thesis: S.M., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2018.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Cataloged from student-submitted PDF version of thesis.Includes bibliographical references (pages 67-74).A central goal in quantum information science is to establish entanglement across multiple quantum memories in a manner that allows individual control and readout of each constituent qubit. In the area of solid state quantum optics, a leading system is the negatively charged nitrogen vacancy center in diamond, which allows access to a spin center that can be entangled to multiple nuclear spins. Scaling these systems will require the entanglement of multiple NV centers, together with their nuclear spins, in a manner that allows for individual control and readout. Here we demonstrate a technique that allows us to prepare and measure individual centers within an ensemble, well below the diffraction limit. The technique relies on optical addressing of spin-dependent transitions, and makes use of the built-in inhomogeneous distribution of emitters resulting from strain splitting to measure individual spins in a manner that is non-destructive to the quantum state of other nearby centers. We demonstrate the ability to resolve individual NV centers with subnanometer spatial resolution. Furthermore, we demonstrate crosstalk-free individual readout of spin populations within a diffraction limited spot by performing resonant readout of one NV during a spectroscopic sequence of another. This method opens the door to multi-qubit coupled spin systems in solids, with individual spin manipulation and readout.by Eric Bersin.S.M

Demonstration of sub-3 ps temporal resolution with a superconducting nanowire single-photon detector

Improvements in temporal resolution of single photon detectors enable increased data rates and transmission distances for both classical and quantum optical communication systems, higher spatial resolution in laser ranging, and observation of shorter-lived fluorophores in biomedical imaging. In recent years, superconducting nanowire single-photon detectors (SNSPDs) have emerged as the most efficient, time-resolving single-photon counting detectors available in the near infrared, but understanding of the fundamental limits of timing resolution in these devices has been limited due to a lack investigations into the time scales involved in the detection process. We introduce an experimental technique to probe the detection latency in SNSPDs and show that the key to achieving low timing jitter is the use of materials with low latency. By using a specialised niobium nitride (NbN) SNSPD we demonstrate that the system temporal resolution can be as good as 2.6±0.2 ps for visible wavelengths and 4.3±0.2 ps at 1550 nm