Quantum Research Seminar: Arnulf Snedker-Nielsen & Noah Kaufmann

Speaker: Arnulf Snedker-Nielsen, Photonics Line, NQCP

Title: Chemistry in a lattice for spin-photon quantum computing

Abstract: Colour centres in silicon have great potential as single photon sources for quantum technologies.  Some of them - like the T centre - also possess long-lived spins that enable natural spin-photon interfaces for quantum computing and communication applications. We introduce these applications and present work on the generation of several types of colour centres in silicon for mass-manufacturable silicon-on-insulator quantum devices. We investigate how different processes in the device development affect the presence of the quantum emitters, including thermal annealing and fabrication steps for optical nanostructures. 

Speaker: Noah Kaufmann, Quantum Optics, NBI

Title: Sensing with qubits in the presence of non-markovian noise

Abstract: Can entanglement help us detect weaker signals in a noisy environment? In an ideal setting, entanglement among sensors allows us to decrease estimation uncertainty compared to using independent sensors. However, noise that affects the sensors can wash out this advantage. In this talk, I will explore when entanglement remains a useful resource for sensing using the example of Ramsey spectroscopy with GHZ and spin-squeezed states in the presence of dephasing noise. I will show that, when the noise is correlated in time or space, entangled sensors can achieve a substantial sensitivity advantage. Entanglement can also improve sensing across a wider range of signal frequencies, and this bandwidth advantage persists even for uncorrelated noise.