In English

Photon generation in a doubly tunable resonator

Ida-Maria Svensson
Göteborg : Chalmers tekniska högskola, 2012. 53 s.
[Examensarbete på avancerad nivå]

In November 2011 the first experimental observation of the dynamical Casimir effect was published [1]. Superconducting circuits were used to show that a single mirror moving in vacuum could generate photons, by parametric amplification of vacuum uctuations. This project is a side track of this research where a second mirror is introduced to investigate photon generation in-between the mirrors. The work includes both theory studies and experimental practice. Resonators have been fabricated on chip in a cleanroom and measured in a dilution refrigerator. The focus has been on how the different boundary conditions of the resonator field affect the photon generation. A superconducting circuit has been used including a = 2/2 resonator with two SQUIDs inducing tunability of the resonance frequency via on-chip ux tuning lines. The two SQUIDs are placed in each end of the cavity in order to simulate moving mirrors. The mirrors are used to modulate the boundary conditions of the cavity. This is done by changing the SQUID inductance which is achieved by applying a magnetic ux to the SQUID loop. Depending on if the mirrors move in or out of phase, a breathing or translational mode can be created in the cavity. Theory predicts photon generation in different modes depending on if the pump frequency is two or three times the resonance frequency [2]. Measurements have been done at a temperature of around 50mK, which is low enough to have a negligible amount of thermal photons and quasi-particles in the cavity. The static tuning of the resonator have been probed by sweeping the uxes applied to the two SQUIDs and at each point the resonance frequency has been extracted. Good results have been achieved and two dimensional tuning is shown. A high frequency, ux modulation have been applied to the SQUIDs both one at a time and simultaneously to generate photons. In the two mirror modulation case qualitative agreement with theory has been observed for driving in the breathing and translational mode respectively. Generation occurs first for the breathing mode at 2*omega (twice the resonance frequency) and for the translational mode at 3*omega.

Nyckelord: resonator, photon generation, tunable, SQUID

Publikationen registrerades 2012-09-20. Den ändrades senast 2015-02-11

CPL ID: 163601

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