Multifrequency sources of quantum correlated photon pairs on-chip: a path toward integrated Quantum Frequency Combs

Abstract

Recent developments in quantum photonics have initiated the process of bringing photonic-quantumbased systems out-of-the-lab and into real-world applications. As an example, devices to enable the exchange of a cryptographic key secured by the laws of quantum mechanics are already commercially available. In order to further boost this process, the next step is to transfer the results achieved by means of bulky and expensive setups into miniaturized and affordable devices. Integrated quantum photonics is exactly addressing this issue. In this paper, we briefly review the most recent advancements in the generation of quantum states of light on-chip. In particular, we focus on optical microcavities, as they can offer a solution to the problem of low efficiency that is characteristic of the materials typically used in integrated platforms. In addition, we show that specifically designed microcavities can also offer further advantages, such as compatibility with telecom standards (for exploiting existing fibre networks) and quantum memories (necessary to extend the communication distance), as well as giving a longitudinal multimode character for larger information transfer and processing. This last property (i.e., the increased dimensionality of the photon quantum state) is achieved through the ability to generate multiple photon pairs on a frequency comb, corresponding to the microcavity resonances. Further achievements include the possibility of fully exploiting the polarization degree of freedom, even for integrated devices. These results pave the way for the generation of integrated quantum frequency combs that, in turn, may find important applications toward the realization of a compact quantum-computing platform.

Universal N -Partite d -Level Pure-State Entanglement Witness Based on Realistic Measurement Settings

“…One case in which these operators cannot be constructed by using stabilizers is for confirming the presence of a qudit quantum state with the experimental restriction of only two-level projection measurements being possible. For example, one can consider a three-level two-photon time-bin entangled state [43][44][45][46][47][48], i.e. |ψ = 1 √ 3 (|0, 0 + |1, 1 + |2, 2 ).…”

Photonic RF spectral filters based on transversal filters with Kerr microcombs of varying free spectral ranges

“…Following the first report of Kerr frequency comb sources in 2007 [48], the first integrated CMOS compatible integrated optical parametric oscillators were reported in 2010 [36,37], and since then this field has exploded [47]. Many cutting-edge applications have been demonstrated based on CMOS-compatible micro-combs, ranging from filter-driven mode-locked lasers [49][50][51][52] to quantum physics [53][54][55][56][57][58]. Most recently, Kerr micro-combs have demonstrated their enormous potential for sources for ultrahigh bandwidth coherent optical fiber communications [59], optical frequency synthesis [60] and many other applications [61][62][63][64][65][66][67][68].…”

Practical system for the generation of pulsed quantum frequency combs

“…The recent demonstration of integrated frequency combs for quantum state generation introduces a possible solution towards addressing this issue [6]. Specifically, these are onchip light sources with a broad spectrum of evenly-spaced frequency modes, and can be emitted from a nonlinear micro-cavity when one of its resonances is optically excited [7].…”