The Optimal Control Approach to Quantum Light Squeezing

Bogdan Mielnik, Jesús Fuentes

Felix Alpman, Rickard Högberg

In this thesis, we examine waveguide phase matching conditions necessary for the generation and detection of squeezed states of light. In particular, the temperature dependence of the nonlinear interactions that generate squeezed light is investigated. The theoretical expressions for the conversion efficiencies of the waveguides and the possible squeezing levels are derived. Both of these expressions are dependent on the difference in phase between the interacting modes of light. The phase difference can be assumed to vary linearly with both temperature and wavelength, hence to achieve and maintain optimal squeezing conditions the temperature of the waveguides needs to be controlled for different wavelengths. To do this, a PTC10 temperature controller from Stanford Research Systems was implemented into the lab setup. The optimal operating temperatures of the waveguides were obtained by characterizing the waveguides and fitting the theoretical expressions to the obtained data points. This was done for the integer wavelengths between 1548-1552 \SI{}{\nano \meter}. The highest measured squeezing level was \SI{0.83}{dB} at \SI{1550}{\nano \meter}. The optimal temperatures were then mapped to their respective wavelength and programmed into the temperature controller. The results revealed an approximately linear relationship between the fundamental wavelength and the optimal operating temperature. Furthermore, the measured behavior agrees well with the theoretical model, demonstrating reliable wavelength dependent tuning of squeezed light generation in a single-pass waveguide platform.

M. D. Reid, Alistair S. Lane, Daniel F. Walls

F. Albarrán-Arriagada, Guillermo Romero, E. Solano +1 more

Quantum noise reduction below the shot-noise limit is a signature of light-matter quantum interaction. A limited amount of squeezing can be obtained along the transient evolution of a two-level system resonantly interacting with a harmonic mode. We propose the use of optimal quantum control over the two-level system to enhance the transient noise reduction in the bosonic mode in a system described by the Jaynes-Cummings model. Specifically, we propose the use of a sequence of Gaussian pulses in a time window where the dissipative effects are negligible. We find that the correct choice of pulse times can reduce the noise in the quadrature field mode well below the shot noise, reaching reductions of over 80%. As the Jaynes-Cummings model describes a pivotal light-matter quantum system, our approach for noise reduction provides an experimentally feasible protocol to produce a nontrivial amount of squeezing with current technology.

Anton Halaski, Matthias G. Krauss, Daniel Basilewitsch +1 more

The authors show how to use optimal control theory to maximize squeezing in an optomechanical setup with two external drives and determine how fast the mechanical mode can be squeezed. The results provide a clear recipe for experimentalists to achieve optimized quantum control in such optomechanical systems.

Hans‐A. Bachor