Michael L. Fanto

On-Chip Quantum Interference from a Single Silicon Ring-Resonator Source

Here we demonstrate quantum interference of photons on a Silicon chip produced from a single ring resonator photon source. The source is seamlessly integrated with a Mach-Zehnder interferometer, which path entangles degenerate bi-photons produced via spontaneous four wave mixing in the Silicon ring resonator. The resulting bi-photon N00N state is controlled by varying the relative phase of the integrated Mach-Zehnder interferometer, resulting in high two-photon interference visibilities of V~96%. Furthermore, we show that the interference can be produced using pump wavelengths tuned to all of the ring resonances accessible with our tunable lasers (C+L band). This work is a key demonstration towards the simplified integration of multiple photon sources and quantum circuits together on a monolithic chip, in turn, enabling quantum information chips with much greater complexity and functionality.

Scalable Hong-Ou-Mandel manifolds in quantum-optical ring resonators

Quantum Information Processing, from cryptography to computation, based upon linear quantum optical circuit elements relies heavily on the ability offered by the Hong-Ou-Mandel (HOM) Effect to route photons from separate input modes into one of two common output modes. Specifically, the HOM Effect accomplishes the path entanglement of two photons at a time such that no coincidences are observed in the output modes of a system exhibiting the effect. In this paper, we prove in principle that a significant increase in the robustness of the HOM Effect can be accomplished in a scalable, readily manufactured nanophotonic system comprised of two waveguides coupled, on chip, to a ring resonator. We show that by operating such a device properly, one can conditionally bunch coincident input photons in a way that is far more robust and controllable than possible with an ordinary balanced beam splitter.

Passively mode-locked InAs quantum dot lasers on a silicon substrate by Pd-GaAs wafer bonding

We demonstrate an electrically pumped InAs quantum dot (QD) two-section passively mode-locked laser (MLL) on a silicon substrate by low temperature (250u2009°C) Pd-GaAs wafer bonding technology. The saturable absorber of the QD-MLL is electrically isolated by a 15-μm wide dry-etching gap which resulted in ∼30u2009kΩ resistance from the gain regions of the MLL. At room temperature, the laser operates in the O-band (1.3u2009μm) telecommunication wavelength regime with a threshold current of 94u2009mA and laser bar cavity and absorber lengths of 6u2009mm and 300u2009μm, respectively. The optimum mode-locked conditions are observed under injection current and reverse bias voltage of 124u2009mA and −7u2009V, which generates pulses at a repetition rate of 7.3u2009GHz, an optical bandwidth of 0.97u2009nm, and a nearly transform limited pulse width of 2u2009ps (sech2 pulse profile). These results enable QD-MLLs to be integrated with silicon photonic integrated circuits, such as optical time division multiplexing and optical clocks.

Efficiently heralded silicon ring resonator photon-pair source

Presented here are results on a silicon ring resonator photon pair source with a high heralding efficiency. Previous ring resonator sources suffered from an effective 50% loss because, in order to generate the photons, the pump must be able to couple into the resonator which is an effective loss channel. However, in practice the optical loss of the pump can be traded off for a dramatic increase in heralding efficiency. This research found theoretically that the heralding efficiency should increase by a factor of ∼ 3:75 with a factor of 10 increase in the required pump power. This was demonstrated experimentally by varying the separation (gap) between the input waveguide and the ring while maintaining a constant drop port gap. The ring (R = 18:5μm, W = 500nm, and H = 220nm) was pumped by a tunable laser (λ ≈ 1550nm). The non-degenerate photons, produced via spontaneous four wave mixing, exited the ring and were coupled to fiber upon which they were filtered symmetrically about the pump. Coincidence counts were collected for all possible photon path combinations (through and drop port) and the ratio of the drop port coincidences to the sum of the drop port and cross term coincidences (one photon from the drop port and one from the through port) was calculated. With a 350nm pump waveguide gap (2:33 times larger than the drop port gap) we confirmed our theoretical predictions, with an observed improvement in heralding efficiency by a factor of ∼ 2:61 (96:7% of correlated photons coupled out of the drop port). These results will enable increased photon flux integrated photon sources which can be utilized for high performance quantum computing and communication systems.

Ultraviolet integrated photonics (Conference Presentation)

Quantum information processing relies on the fundamental property of quantum interference, where the quality of the interference directly correlates to the indistinguishability of the interacting particles. The creation of these indistinguishable particles, photons in this case, has conventionally been accomplished with nonlinear crystals and optical filters to remove spectral distinguishability, albeit sacrificing the number of photons. This research describes the use of an integrated aluminum nitride microring resonator circuit to selectively generate photon pairs at the narrow cavity transmissions, thereby producing spectrally indistinguishable photons in the ultraviolet regime to interact with trapped ion quantum memories. The spectral characteristics of these photons must be carefully controlled for two reasons: (i) interference quality depends on the spectral indistinguishability, and (ii) the wavelength must be strictly controlled to interact with atomic transitions. The specific ion of interest for these trapped ion quantum memories is Ytterbium which has a transition at 369.5 nm with 12.5 GHz offset levels. Ytterbium ions serve as very long lived and stable quantum memories with storage times on the order of 10’s of minutes, compared with photonic quantum memories which are limited to 10-6 to 10-3 seconds. The combination of the long lived atomic memory, integrated photonic circuitry, and the photonic quantum bits are necessary to produce the first quantum information processors. In this article, I will present results on wavelength operation, dispersion analysis, and second harmonic generation in aluminum nitride waveguides.

Wide-bandgap integrated photonic circuits for interfacing with quantum memories (Conference Presentation)

Quantum information processing relies on the fundamental property of quantum interference, where the quality of the interference directly correlates to the indistinguishability of the interacting particles. The creation of these indistinguishable particles, photons in this case, has conventionally been accomplished with nonlinear crystals and optical filters to remove spectral distinguishability, albeit sacrificing the number of photons. This research describes the use of an integrated aluminum nitride microring resonator circuit to selectively generate photon pairs at the narrow cavity transmissions, thereby producing spectrally indistinguishable photons in the ultraviolet regime to interact with trapped ion quantum memories. The spectral characteristics of these photons must be carefully controlled for two reasons: (i) interference quality depends on the spectral indistinguishability, and (ii) the wavelength must be strictly controlled to interact with atomic transitions. The specific ion of interest for these trapped ion quantum memories is Ytterbium which has a transition at 369.5 nm with 12.5 GHz offset levels. Ytterbium ions serve as very long lived and stable quantum memories with storage times on the order of 10’s of minutes, compared with photonic quantum memories which are limited to 10-6 to 10-3 seconds. The combination of the long lived atomic memory, integrated photonic circuitry, and the photonic quantum bits are necessary to produce the first quantum information processors. In this seminar, I will present results on ultraviolet wavelength operation, dispersion analysis, and propagation loss in aluminum nitride waveguides.

Quantifying record entanglement in extremely large Hilbert spaces with adaptively sampled EPR correlations

As applications of quantum information and processing grow in scale in sophistication, the ability to quantify the resources present in very high-dimensional quantum systems is an important experimental problem needing solution. In particular, quantum entanglement is a resource fundamental to most applications in quantum information, but becomes intractable to measure in high dimensional systems, both because of the difficulty in obtaining a complete description of the entangled state, and the subsequent calculation of entanglement measures. In this paper, we discuss how one can measure record levels of entanglement simply using the same correlations employed to demonstrate the EPR paradox. To accomplish this, we developed a new entropic uncertainty relation where the Einstein-Podolsky-Rosen (EPR) correlations between positions and momenta of photon pairs bound quantum entropy, which in turn bounds entanglement. To sample the EPR correlations efficiently, one can sample at variable resolution, and combine this with relations in information theory so that only regions of high probability are sampled at high resolution, while entanglement is never over-estimated. This approach makes quantifying extremely high-dimensional entanglement scalable, with efficiency that actually improves with higher entanglement.

Silicon Photonic wafer fabrication for education

Silicon Photonics is a promising new technology for realizing efficient, high performance interconnects. There is a growing need for educating future engineers on how to design, fabricate, test and package Silicon photonic circuits. Here we demonstrate a Silicon photonic process suitable for an educational institution with i-line lithography capabilities. We have developed a suitable process for realizing passive photonic devices (i.e. waveguides, interferometric structures and fiber-chip grating couplers). The process is realized in a CMOS compatible environment which has been in use since 1986 to teach microelectronic engineering. And is now also being used to support the AIM Photonics Academy education mission. Specifically, an array of TM-polarized grating couplers with a ring resonator was fabricated with a lithographic resolution of 0.325 µm on an SOI wafer. The setup time and run time required was 3 days in comparison to the long wait time in the industry. Optimization of the resolution using ARC i-CON-7, diluted OiR 620 and the etch selectivity of the Silicon to the 1∶1 OiR 620:PGMEA was key to the student run fabrication process and is supported by the Optical microscope and SEM results.

Silicon photonic wafer fabrication for education

Silicon Photonics is a promising new technology for realizing efficient, high performance interconnects. There is a growing need for educating future engineers on how to design, fabricate, test and package Silicon photonic circuits. Here we demonstrate a Silicon photonic process suitable for an educational institution with i-line lithography capabilities. We have developed a suitable process for realizing passive photonic devices (i.e. waveguides, interferometric structures and fiber-chip grating couplers). The process is realized in a CMOS compatible environment which has been in use since 1986 to teach microelectronic engineering. And is now also being used to support the AIM Photonics Academy education mission. Specifically, an array of TM-polarized grating couplers with a ring resonator was fabricated with a lithographic resolution of 0.325 µm on an SOI wafer. The setup time and run time required was 3 days in comparison to the long wait time in the industry. Optimization of the resolution using ARC i-CON-7, diluted OiR 620 and the etch selectivity of the Silicon to the 1∶1 OiR 620:PGMEA was key to the student run fabrication process and is supported by the Optical microscope and SEM results.

Measurement of Quantum Interference in a Silicon Ring Resonator Photon Source

Silicon photonic chips have the potential to realize complex integrated quantum information processing circuits, including photon sources, qubit manipulation, and integrated single-photon detectors. Here, we present the key aspects of preparing and testing a silicon photonic quantum chip with an integrated photon source and two-photon interferometer. The most important aspect of an integrated quantum circuit is minimizing loss so that all of the generated photons are detected with the highest possible fidelity. Here, we describe how to perform low-loss edge coupling by using an ultra-high numerical aperture fiber to closely match the mode of the silicon waveguides. By using an optimized fusion splicing recipe, the UHNA fiber is seamlessly interfaced with a standard single-mode fiber. This low-loss coupling allows the measurement of high-fidelity photon production in an integrated silicon ring resonator and the subsequent two-photon interference of the produced photons in a closely integrated Mach-Zehnder interferometer. This paper describes the essential procedures for the preparation and characterization of high-performance and scalable silicon quantum photonic circuits.