Covariance matrix reconstruction of nonclassical light generated in an on-chip optical parametric oscillator

Abstract

The increasing development of novel quantum technologies encourages the research in nonclassical states sources, being quantum correlated light one of the main resources for several applications of quantum mechanics. Silicon based integrated systems present huge potential for the further development of optical quantum communication, as they are compatible with microelectronic devices and telecommunication band wavelengths. The current capability of low loss waveguides production plus strong nonlinear coefficients makes this platform ideal for the generation of nonclassical states. Integrated microcavities can be tailored to act as low threshold optical parametric oscillators, where intense signal and idler modes are easily excited. Due to the parametric character of the physical process responsible for these oscillations, strong correlations are expected between the generated modes. We use resonator assisted detection systems to reconstruct the covariance matrices of the generated continuous variables states in order to retrieve the full quantum description of the system. Up to our knowledge, this is the first full tomography of states generated in an integrated third order optical parametric oscillator operating above threshold.

Sideband four-mode entanglement in a Four-wave mixing process

“…For instance, the excess of noise could induce some undesired electronic response, any mismatch between the resonator and the light beam would contaminate the measurements or any fluctuation in the phase from the demodulation channels would struggle the detection as well. An example of this can be found in the PhD thesis from Kögler 24 , where he studied and OPO on-chip and implemented the resonator detection for the description of the state. During this section we will address this issues and present the implemented solution.…”

“…Nonetheless, this configuration had two drawbacks. At lower temperature the gain was not enough to overcome the safety lower limit (electronic level figures 23,24) and at high temperature the quantum correlations were weak. The second configuration presented a ratio of 0.46 between the seed and the pump waist, increasing the light atom interaction.…”

“…A second system generates correlated states via Four-Wave Mixing based on chip. Chips work at room temperature and can be coupled to the current telecommunication technologies given that their spectrum is in the infrared (1500 nm), representing an advantage for its implementation [24]. Finally, we implemented an OPO based on rubidium vapor cell and reconstruct the covariance matrix, finding that the output modes of the system were entangled [25].…”