The necessity for scalable, reliable and reproducible quantum systems is raising in the time for appealing potentialities in application of this technology. On-chip photonic solutions are a leading competitor by combining established classical fabrication technologies, integrated photonics and quantum optical effects. Lithium Niobate on insulator (LNOI) is one of the main contenders for the integration of on-chip functionality. Rare Earth Ions (REI) already proved many different good properties in term of optical and spin features as well as good integration through implantation. In particular, 171Ytterbium showed to have clock transitions in the zero phonon line at zero field which would screen magnetic noise from high spin materials. Here the possibility to create a reconfigurable interferometer on-chip by the employment of fabrication techniques has been showed with the creation of LN structures, interconnecting infrastructure and far field coupling from SU8 resist. Moreover, doping Lithium niobate photonic crystal cavities has been investigated to be employed as switchable single photon sources.
The necessity for scalable, reliable and reproducible quantum systems is raising in the time for appealing potentialities in application of this technology. On-chip photonic solutions are a leading competitor by combining established classical fabrication technologies, integrated photonics and quantum optical effects. Lithium Niobate on insulator (LNOI) is one of the main contenders for the integration of on-chip functionality. Rare Earth Ions (REI) already proved many different good properties in term of optical and spin features as well as good integration through implantation. In particular, 171Ytterbium showed to have clock transitions in the zero phonon line at zero field which would screen magnetic noise from high spin materials. Here the possibility to create a reconfigurable interferometer on-chip by the employment of fabrication techniques has been showed with the creation of LN structures, interconnecting infrastructure and far field coupling from SU8 resist. Moreover, doping Lithium niobate photonic crystal cavities has been investigated to be employed as switchable single photon sources.
Electro-optical control of on-chip photonic devices is an essential tool for efficient integrated photonics. Lithium niobate on insulator (LNOI) is an emerging platform for on-chip photonics due to its large electro-optic coefficient and high nonlinearity. Integrating quantum emitters into LNOI would extend their versatility in classic photonics to quantum computing and communication. Here, we incorporate rare-earth ion (REI) quantum emitters into electro-optical tunable lithium niobite (LN) thin films and demonstrate control of LN microcavities coupled to REIs over a frequency range of 160 GHz with 5 µs switching speed. Dynamic control of the cavities enables modulation of the Purcell enhancement of REIs with short time constants. Using Purcell enhancement, we show evidence of detecting single Y b 3 + ions in LN cavities. Coupling quantum emitters in fast tunable photonic devices is an efficient method to shape the waveform of the emitter. It also offers a platform to encode quantum information in the integration of a spectral–temporal–spatial domain to achieve high levels of channel multiplexing, as well as an approach to generate deterministic single-photon sources.
Quantum photonics provides a powerful toolbox with vast applications ranging from quantum simulation, photonic information processing, all optical universal quantum computation, secure quantum internet as well as quantum enhanced sensing. Many of these applications require the integration of several complex optical elements and material systems which pose a challenge to scalability. It is essential to integrate linear and non-linear photonics on a chip to tackle this issue leading to more compact, high bandwidth devices. In this thesis we demonstrate a pathway to achieving several components in the quantum photonic toolbox on the same integrated photonic platform. We focus particularly on two of the more nontrivial components, a single photon source and an integrated quantum light-matter interface. We address the problem of a scalable, chip integrated, fast single photon source, by using atomically thin layers of 2D materials interfaced with plasmonic waveguides. We further embark on the challenge of creating a new material system by integrating rare earth ions with the emerging commercial platform of thin film lithium niobate on insulator. Rare earth ions have found widespread use in classical and quantum information processing. However, these are traditionally doped in bulk crystals which hinder their scalability. We demonstrate an integrated photonic interface for rare earth ions in thin film lithium niobate that preserves the optical and coherence properties of the ions. This combination of rare earth ions with the chip-scale active interface of thin film lithium niobate opens a plethora of opportunities for compact optoelectronic devices. As an immediate application we demonstrate an integrated optical quantum memory with a rare earth atomic ensemble in the thin film. The new light matter interface in thin film lithium niobate acts as a key enabler in an already rich optical platform representing a significant advancement in the field of integrated quantum photonics.
Electro-optical control of on-chip photonic devices is an essential tool for efficient integrated photonics. Lithium niobate on insulator (LNOI) is an emerging platform for on-chip photonics due to its large electro-optic coefficient and high nonlinearity [1]. Integrating quantum emitters into LNOI would extend their versatile use in classic photonics to quantum computing and communication [2, 3]. Here, we incorporate single rare-earth ions (REI) quantum emitters in electro-optical tunable lithium niobite (LN) thin films and demonstrate control of LN microcavities coupled to REI over a frequency range of 160 GHz with 5 \mus switching speed. Dynamical control of the cavities enables the modulation of the Purcell enhancement of the REIs with short time constants. Using the Purcell enhancement, we show evidence of detecting single Yb3+ ions in LN cavities. Coupling quantum emitters in fast tunable photonic devices is an efficient method to shape the waveform of the emitter [4]. It also offers a platform to encode quantum information in the integration of a spectral-temporal-spatial domain to achieve high levels of channel multiplexing, as well as an approach to generate deterministic single-photon sources [5, 6].
Lithium niobate on insulator (LNOI), thanks to its electro-optic properties and second order nonlinearity, is one of the most promising photonic materials for on-chip implementation of a complex photonic integrated circuit (PIC) [1]. Integration of rare earth ion emitters (RIE), characterized by high coherent transitions in both optical and microwave domains, into LNOI is a very attractive perspective to fully exploit the potential of this material in quantum optics applications and for on chip light generation and amplification. By choosing Erbium ions these functionalities can be implemented at telecom wavelengths (~1550 nm). Erbium integration in LNOI can be achieved using the smart cut technique [2]. However, this approach implies heating the material up to ~1100 °C, approaching the Curie temperature of lithium niobate (~1200 °C). Ion implantation also permits the incorporation of RIE into the lithium niobate (LN) crystal structure, operating at lower temperature with high spatial precision of the doped region in a complex PIC.
Rare-earth ion ensembles doped in single crystals are a promising materials system with widespread applications in optical signal processing, lasing, and quantum information processing. Incorporating rare-earth ions into integrated photonic devices could enable compact lasers and modulators, as well as on-chip optical quantum memories for classical and quantum optical applications. To this end, a thin film single crystalline wafer structure that is compatible with planar fabrication of integrated photonic devices would be highly desirable. However, incorporating rare-earth ions into a thin film form-factor while preserving their optical properties has proven challenging. We demonstrate an integrated photonic platform for rare-earth ions doped in a single crystalline thin film lithium niobate on insulator. The thin film is composed of lithium niobate doped with Tm 3+ . The ions in the thin film exhibit optical lifetimes identical to those measured in bulk crystals. We show narrow spectral holes in a thin film waveguide that require up to 2 orders of magnitude lower power to generate than previously reported bulk waveguides. Our results pave the way for scalable on-chip lasers, optical signal processing devices, and integrated optical quantum memories.
Quantum photonics has advanced rapidly and become a leading approach for developing a broad range of quantum technologies, including quantum communications, quantum information processing, quantum computing, and quantum sensing. Besides, the emerging photonic integrated circuits (PIC) technology has been widely used to implement versatile optical elements advantageous for different quantum applications. For example, PIC-based devices have functioned as building blocks, such as photonic qubit sources, linear optical circuits, modulators, and even single-photon detectors, for realizing highly integrated, large-scale quantum computing schemes. In such a powerful quantum photonic integrated circuits (QPIC) scheme, the creation, manipulation, and testing of quantum entanglement states from the generated qubits via a reconfigurable photonic circuitry are essential. Though the state-of-the-art PIC technology is established based on Si photonics due to its widely mature nanophotonic circuit (waveguide) fabrication technology supported by the existing immense semiconductor industry, Si-based PIC has limitations in implementing efficient and fast active elements that usually demand a quadratic nonlinearity. Lithium niobate (LN), renowned as “the silicon of photonics”, has long been a popular material widely used in integrated-optical and nonlinear-optical applications. A great variety of passive and active photonic elements have been realized in the LN platform. Recently, a novel material based on high-quality single-crystalline films of LN, known as thin-film LN on insulator (LNOI), has been developed and has soon drawn enormous attention for its greatly promising ability to realize nanoscale PIC/QPIC in this iconic optical material platform. In this presentation, we report our recent studies on several key LN PIC building blocks for developing novel quantum photonic sources and circuits, including highly integrated photonic-circuit periodically poled lithium niobate (PPLN) chips for photon-pair generation and manipulation, for high-dimensional frequency-entangled qudit production, for time-frequency grid-state generation, for continuous-variable squeezed vacuum state generation, and their potential applications to quantum computing/communication/sensing technology. Besides, a PP-LNOI electro-optic (EO) polarization mode converter (PMC) useful for demonstrating fast control of quantum polarization states and other LNOI circuit elements as QPIC building blocks will also be presented.