The recent developments of optoelectronics do promote the progress in many other fields. For quantum information processing, we made efforts in manufacturing quantum devices by using optoelectronic techniques. We designed quantum dot embedded nanocavities to serve as efficient quantum emitters; using spectral multiplexing technique, we fabricated a heralded single-photon source, emitting highly pure and speedy single photons; and defects in GaN were observed serving as room temperature quantum random number generators. An entangled photon emitter with visibility of 97% was developed using cascaded second-order nonlinear optical process in PPLN waveguides; and Si3N4 microrings were effectively applied to establish photon entanglers. Readout circuits were optimized to fabricate specific single-photon avalanche detectors, and telecomm-band single-photon avalanche detectors have been improved to 128 × 32 arrays for quantum imaging. A multiplexed quantum memory was explored to simultaneously store 1650 single photons. Opto-electro-mechanical devices were studied or fabricated in order to measure minor quantities in quantum level. These works may shed light on quantum information technology for the future.
The recent developments of optoelectronics do promote the progress in many other fields. For quantum information processing, we made efforts in manufacturing quantum devices by using optoelectronic techniques. We designed quantum dot embedded nanocavities to serve as efficient quantum emitters; using spectral multiplexing technique, we fabricated a heralded single-photon source, emitting highly pure and speedy single photons; and defects in GaN were observed serving as room temperature quantum random number generators. An entangled photon emitter with visibility of 97% was developed using cascaded second-order nonlinear optical process in PPLN waveguides; and Si3N4 microrings were effectively applied to establish photon entanglers. Readout circuits were optimized to fabricate specific single-photon avalanche detectors, and telecomm-band single-photon avalanche detectors have been improved to 128 × 32 arrays for quantum imaging. A multiplexed quantum memory was explored to simultaneously store 1650 single photons. Opto-electro-mechanical devices were studied or fabricated in order to measure minor quantities in quantum level. These works may shed light on quantum information technology for the future.
Lithium niobate (LiNbO3) serves as one of the most competitive materials in nonlinear integrated photonics and becomes a key platform for the realization of integrated optical quantum technology, because it is physically and chemically very stable and it has a larger refractive index, a wider transparent wavelength range and better nonlinear optical characteristics than most of the traditional materials. Using the second-order nonlinear effect of periodically polarized lithium niobate (PPLN) crystal, single-photon frequency conversion was successfully realized to satisfy the quantum measurement requirements. LiNbO3and PPLN Waveguides were widely developed to solve the problems such as easy beam divergence in crystals, so that the improved nonlinear conversion effect promotes the successful fabrication of many quantum devices such as single photon sources, entangled photon sources and single photon detectors etc. By combining LiNbO3waveguides with other waveguide technologies, one can fabricate various LiNbO3integrated optical components serving as the core devices of quantum interfaces, quantum memories and etc. Based on these progresses, we see the attractive potential of LiNbO3material to play a deterministic role in quantum information technology.
Abstract In photonic quantum information processing, the generation, manipulation, and detection of photonic quantum states inherently depend on electronic control devices. As a core enabling technology, on-chip optoelectronic hybrid integration drives optical quantum devices toward higher density, lower power consumption, and enhanced stability while pushing the application and performance limits of quantum information processing. This review summarizes the progress in chip-integrated optoelectronic technologies and their applications in key quantum information scenarios-quantum communication, quantum photonic source engineering, optical frequency conversion, and linear optical quantum information processing. We also discuss key challenges and future directions, envisioning optoelectronic integration as the pivotal bridge from lab demonstrations to practical, scalable quantum photonic systems.
In the past decades quantum optics has been at the forefront of quantum innovative technologies. For practical applications, scalable platforms for implementation of quantum optical circuits are vital. This thesis presents two new platforms for scalable implementation of quantum optical circuits, namely, modular approach and monolithic integration. Here, we take the first steps towards the integration of three main elements of every quantum optics circuits: Single-photon emitters, single-photon detectors, and quantum logics. Until now, most quantum optical circuits used separate platforms for single-photon generation and detection. The main challenge in the integration of these technologies, which have different requirements, has slowed down the research in the field. Here, we integrate sources and detectors by first fabricating the devices on their own platform and then transferring and combining them together. Plasma enhanced chemical vapor deposition of silicon nitride followed by etching optical waveguides connect these elements. Removing the Poissonian optical excitation field from the quantum circuit is necessary for integration. Classical optical excitation can be avoided if the sources are electrically pumped. However, fabrication of high-quality electrically pumped sources, suitable for integration, has been limited. The experiments described in chapter 4 are our first step towards addressing the mentioned problem. Defect-free nanowires are grown on <100> direction and their optoelectronic performance are characterized. Nanowire quantum dots, thanks to their waveguiding, purity, coherence and their potentials for deterministic integration with other optical circuits, are promising single-photon sources for on-chip quantum optics. However, precise control of the emission energy of the quantum dots by growth has not become possible yet. Chapter 5 describes a method for on-chip tuning of emission energy of nanowire quantum dots using strain fields. We show the emission energy of independent nanowire quantum dots can be brought into degeneracy without affecting their single-photon emission properties. The quantum optical components have to be routed and connected together to form functional circuits. On a chip, this is usually carried out using optical waveguides. Moreover, manipulation of single photons has to be done in a scalable fashion. Again optical waveguides and ring resonators are very good candidates for this task. Therefore, understanding the behavior of these circuits such as their losses, polarization dependence, and temperature behavior is important. The experiment described in chapter 6 studies the behavior of plasma enhanced silicon nitride waveguides in cryogenic temperatures. We concluded in this chapter that due to weak thermo-optic sensitivity of silicon nitride at cryogenic temperatures, the available thermal budget on the system should be carefully considered. An important step in achieving a scalable platform for quantum optical circuits is deterministic and efficient integration of single-photon sources. In chapter 7, we demonstrate successful integration of III-V nanowire quantum dots with silicon nitride waveguides. The nanowires are deterministically selected and transferred from the original growth chip to the new substrate where they are integrated with low-loss silicon nitride waveguides. Our measurements show that the integrated sources preserve their high quality emission properties. In chapter 8, we describe an alternative approach: amodular method for scalable quantum optics. The proposed technique is based on coupling the single-photon from sources into optical fibers where the photons can be processed and then fed into the single-photon detectors. This approach has high flexibility and is easier to implement but as described in the chapter, at the moment, losses in the interfaces between optical fibers and single-photon sources are a major limiting factor. We conclude the thesis with some possible future directions and exciting new results on integration of single-photon detectors with sources and waveguides. Finally, primary results on on-chip single-photon filtering and removal of the optical excitation field are demonstrated.
Quantum-photonic chips, which integrate quantum light sources alongside active and passive optical elements, as well as single-photon detectors, show great potential for photonic quantum information processing and quantum technology. Mature semiconductor nanofabrication processes allow for scaling such photonic integrated circuits to on-chip networks of increasing complexity. Second-order nonlinear materials are the method of choice for generating photonic quantum states in the overwhelming majority of linear optic experiments using bulk components, but integration with waveguide circuitry on a nanophotonic chip proved to be challenging. Here, we demonstrate such an on-chip parametric down-conversion source of photon pairs based on second-order nonlinearity in an aluminum-nitride microring resonator. We show the potential of our source for quantum information processing by measuring the high visibility anti-bunching of heralded single photons with nearly ideal state purity. Our down-conversion source yields measured coincidence rates of 80 Hz, which implies MHz generation rates of correlated photon pairs. Low noise performance is demonstrated by measuring high coincidence-to-accidental ratios. The generated photon pairs are spectrally far separated from the pump field, providing great potential for realizing sufficient on-chip filtering and monolithic integration of quantum light sources, waveguide circuits and single-photon detectors. A chip-based source of photon pairs for applications in quantum information processing has been built by a team of scientists in the US. Xiang Guo and co-workers from Yale University built the quantum light source from an aluminum nitride microring resonator. The strong second-order nonlinearity of the aluminum nitride yields efficient parametric down-conversion. This allows 775-nm-wavelength pump photons to be converted into a pair of entangled photons in the telecommunications window of 1550 nm. Tests indicated that the heralded photons generated by the microring source are anti-bunched and have high visibility and a high purity of state, indicating that they are highly suitable for use in quantum optics experiments. In principle, the on-chip source is compatible with megahertz generation rates and large-scale manufacture of integrated optical circuits.