Erik Svanberg

PAD for applied physics 2025.

My research focuses on optical squeezed light sources. The noise of regular laser light or 'coherent' light, is constrained by the uncertainty principle. For such light, the uncertainty in amplitude and phase quadrature is equal and the product of the two is minimal. Squeezed light redistributes this noise, by lowering the noise in one quadrature and increasing it in the other.

Now imagine a sensor that reads out only the phase difference of two interfering light fields. Using regular laser light the uncertainty coming from the uncertainty principle can be a limiting factor, however by using phase squeezed light this limitation can be surpassed, providing a better signal-to-noise ratio than otherwise possible with classical fields.

This uncertainty exists even in the absence of light, the 'vacuum' state. We can overcome this by using 'squeezed vacuum', which again redistributes the noise in the amplitude and phase quadratures. These light fields are used in gravitational wave detectors and we wish to apply them to biosensors as well as continous variable quantum key distribution.

The squeezed light sources I currently work on use waveguides, are integrated into optical fibres, and provide squeezed light around 1550 nm. This provides the advantage of straightforward integration into optical fibre communication networks, as well as increased mode stability due to the single-mode nature of the optical fibres.