OptoElectronics and Communications Conference and International Conference on Photonics in Switching and Computing (OECC/PSC)
Hybrid Photonic Integrated Circuits for Quantum Communications
Moritz Kleinert, Jakob Reck, P. S. Ott, Sarah Simon, Lennart Jehle, Ben Schuler, Martin Kresse, Tianwen Qian, Klara Mihov, Csongor Keuer, Madeleine Weigel, Philipp Winklhofer, Laurids von Emden, Crispin Zawadzki, David de Felipe, Norbert Keil, Martin A. Schell
Compact, high-performance hybrid photonic integrated circuits (PICs) are crucial for advancing Quantum Communications. This paper presents recent examples from the PolyBoard platform, including a time-bin interferometer, a DV-QKD transmitter, and a heralded single photon source. Keywords: Quantum communication and quantum cryptography, Photonic integration, Photonic integrated circuits, Planar lightwave circuits (PLCs), Photonic quantum communication, Single-photon and quantum entangled photon-pair sources
Compact, high-performance hybrid photonic integrated circuits (PICs) are crucial for advancing Quantum Communications. This paper presents recent examples from the PolyBoard platform, including a time-bin interferometer, a DV-QKD transmitter, and a heralded single photon source. Keywords: Quantum communication and quantum cryptography, Photonic integration, Photonic integrated circuits, Planar lightwave circuits (PLCs), Photonic quantum communication, Single-photon and quantum entangled photon-pair sources
Quantum communication promises unconditional security by leveraging the fundamental laws of quantum physics, which make eavesdropping detectable through the disturbance it introduces in quantum states. A cornerstone of this technology is quantum key distribution (QKD), enabling the distribution of a shared secret key between distant users with information- theoretic security, rather than relying on assumptions about an eavesdropper’s computational power, as in classical cryptography. However, current QKD systems rely largely on bulk-optical solutions, which limits scalability, stability, and integration into existing telecommunication infrastructures. Photonic integrated circuits (PICs) offer a promising platform to overcome these challenges by providing compact, stable, and CMOS-compatible architectures. This PhD work investigates integrated photonic platforms for practical quantum communication at telecommunication wavelengths, with a focus on demonstrating QKD protocols across three different encoding schemes: time-bin, frequency-bin, and path. First, a time-bin QKD receiver using a borosilicate-glass integrated imbalanced Mach–Zehnder interferometer (iMZI) is developed and compared with a fiber-based receiver, showing enhanced phase stability and improved long-distance secure key rates. Next, frequency-bin entanglement-based QKD is implemented using silicon microring resonators, demonstrating high-visibility quantum interference and active phase-stabilization techniques. Finally, a chip-to-chip path-entangled QKD link is realized using silicon photonic spiral sources, representing a crucial step toward fully integrated quantum transceivers. Across these experiments, this PhD thesis establishes a unified experimental framework for integrated QKD and evaluates performance in terms of quantum bit error rate, secure key rate, and system stability under realistic operating conditions. Together, the results provide a proof-of-concept demonstration of scalable, high-performance quantum communication using PIC technology, advancing toward practical deployment in future quantum networks and laying foundations for multidimensional and fully integrated quantum communication nodes.
There has been a strong interest to translate optical quantum technologies into photonic integrated circuits (PICs) as they could provide a stable, compact, and potentially scalable architecture for generating, manipulating, and measuring optical quantum states. Among the various PIC technologies that are being developed, silicon-on-insulator (SOI) PICs have several advantages, including technologically mature foundry fabrication, CMOS-process integration, and high-performance switches, modulators, polarization control, filters, and other essential optical components. However, several components are missing that are needed for quantum information processing tasks. Here, we describe recent progress on augmenting SOI PICs with essential capabilities for photonic quantum technologies — entangled photon sources, single photon detectors, and reconfigurable linear optics unitary transformations — and focus on two central application areas: quantum communications and quantum simulation.
Abstract High-dimensional quantum entanglement is an important resource for emerging quantum technologies such as quantum communication and quantum computation. The scalability of metres-long experimental setups limits high-dimensional entanglement in bulk optics. Advancements in quantum technology hinge on reproducible, and reconfigurable quantum devices—including photon sources, which are challenging to achieve in a scalable manner using bulk optics. Advances in nanotechnology and CMOS-compatible integration techniques have enabled the generation of entangled photons on millimeter-scale chips, significantly enhancing scalability, stability, replicability, and miniaturization for real-world quantum applications. In recent years we have seen several chip-scale demonstrations with different discrete degrees of freedom including path, frequency-bin, time-bin, and transverse modes, on many material platforms. A complete quantum photonic integrated circuit requires the generation, manipulation, and detection of quantum states, involving various active and passive quantum photonic components which further increase the degree of complexity. Here, we focus on the high-dimensional versions of qubits—qudits—and review the nonlinear optical processes that facilitate on-chip high-dimensional entangled photon sources, and the currently used material platforms. We discuss a range of current implementations of on-chip high-dimensional entangled photon sources and demonstrated applications. We comment on the current challenges due to the limitations of individual material platforms and present future opportunities in hybrid and heterogeneous integration strategies for the next generation of integrated quantum photonic chips.
For the establishment of secure communication as well as a future quantum internet, technologies like Quantum Key Distribution (QKD) must become smaller in size, cost-effective in production and more performant. Since attacks like store-now-decrypt-later are already a threat for sensitive data, research in this area must be pushed towards a higher practicality. In this work we show the feasibility of using a photonic integrated circuit (PIC) for application as a QKD transmitter. The PIC (provided by Eindhoven University of Technology) comprises a ring laser source, a Mach-Zehnder interferometer (MZI) with integrated RF phase modulators used for pulse carving and phase modulation as well as an attenuator section. This indium phosphide (InP) chip enables us to generate the necessary states for a 4-state time-bin-phase BB84 protocol [1] implementation. After characterization of all the photonic components and preliminary testing, we were able to generate a secret key rate of approximately 89kbps for 50MHz signal repetition rate with a QBER of 1.3% (in Z-Basis) in a back-to-back configuration.
Quantum computing shows great potential in solving highly complex computational challenges in multiple applications, including artificial intelligence, chemical modelling, biology simulation, portfolio optimization, drug delivery, logistical planning, etc. Quantum networking can enable secure communication as well as scalable interconnects of multiple quantum processing units. We need to scale up the number of high-quality qubits and make quantum systems more compact, robust, and lower cost to further improve the performance of quantum computing and networking. Photonic integrated circuits (PICs) can play a significant role in reducing the size, improving the stability, and reducing the system bring-up time of optical subsystems. QuEra’s recent progress shows the potential of leveraging PICs as a viable solution to facilitate the builds of highly scalable and high-performance quantum computers [1]. These results position integrated photonics as a critical enabling technology for next-generation large-scale quantum systems and invite broader participation from the photonics community in advancing quantum technologies with significant industrial impact.