Physics department seminar-FR

Event date(s): February 15, 2024
Time(s): 01:15 PM - 02:15 PM
Category: Fredericton
Location: Fredericton

Join us for the weekly Physics seminar series, featuring Tim Hunt.

Date: Feb 15, 1:15-2:15 p.m.

Location: Toole Hall, Room 3

Speaker: Tim Hunt

Title: A microwave synthesizer for quantum sensing using ultracold atoms

Abstract: Atom interferometers are quantum sensors that can make use of slow-moving, cold atoms to investigate accelerations that the atoms experience, allowing for high precision tools such as gravimeters and gyroscopes. The synthesizer introduced is used for producing laser frequency sidebands for both cooling rubidium atoms and inducing Raman transitions that function as momentum-transfer pulses in our atom interferometer. During these pulses, the phase of the laser is directly imprinted on the atomic wavefunction. Thus, for high-sensitivity quantum measurements, extremely low noise levels are required for the microwave signal phase. The synthesizer design generates two independent microwave signals: one at ~6.6 GHz that acts as a repump frequency for laser cooling down to micro-kelvin temperatures, and one at 6.834 GHz in accordance with the ground state hyperfine splitting in rubidium-87. Using direct digital synthesis, independent control of the frequency, phase, and amplitude of these two signals on microsecond timescales has been achieved. A combined microwave signal is sent to an electro-optic phase modulator to generate the desired optical frequencies in our 780 nm laser system. Measurements of the microwave power spectral density at 6.834 GHz yield a phase noise of -69 dB∙rad²/Hz at an offset of 10 Hz. For a Mach-Zehnder-type atom interferometer with a free-fall time of T = 100 ms, the corresponding estimated measurement noise of 4.3E-9 g in a quantum gravimeter. Improvements of the optical and experimental setup have been required along the way to pursue the characterization of the synthesizer and its effects on the atom interferometer.

Building: Toole Hall

Room Number: 3