Poster Presentations

Poster TitlePoster AbstractPresenter
Indistinguishable photons from an artificial atom in silicon photonicsSilicon is the ideal material for building electronic and photonic circuits at scale. Spin qubits and integrated photonic quantum technologies in silicon offer a promising path to scaling by leveraging advanced semiconductor manufacturing and integration capabilities. However, the lack of deterministic quantum light sources, two-photon gates, and spin-photon interfaces in silicon poses a major challenge to scalability. In this work, we show a new type of indistinguishable photon source in silicon photonics based on an artificial atom. We show that a G center in a silicon waveguide can generate high-purity telecom-band single photons. We perform high-resolution spectroscopy and time-delayed two-photon interference to demonstrate the indistinguishability of single photons emitted from a G center in a silicon waveguide. Our results show that artificial atoms in silicon photonics can source highly coherent single photons suitable for photonic quantum networks and processors.Lukasz Komza
Frequency-Bin Encoding for Quantum NetworkingFrequency-bin encoding—in which quantum information is carried by photons in superpositions of discrete spectral modes—is perfectly suited for transmission and multiplexing in optical fiber, with scalable gate synthesis possible via the quantum frequency processor. Here I summarize recent experimental results on the generation, manipulation, and characterization of frequency-encoded photons tailored for quantum communications, including production of all four Bell states, demonstration of a Bell state analyzer, and record-high-dimensional tomography of on-chip entangled frequency-bin qudits. These results contribute to an expanding toolkit for quantum networks leveraging this promising paradigm for information encoding and multiplexing.Joseph Lukens
Piezoelectric control of spin quantum memories in a cryogenic programmable photonic circuit platformGroup-IV-vacancy color centers diamond are leading spin-photon interfaces in proposed quantum networking and modular quantum computing architectures, due to long-lived spin ground states and coherent optical transitions in nano-structured diamond. A central challenge towards useful applications lies in scaling to large numbers of integrated color centers, with precise, individual control of their ground state manifolds. Here, we introduce a control method based on piezoelectric actuation that has low energy consumption (<10 nJ/strain switching energy), control bandwidth from DC to several GHz, small device footprint, and vanishing cross talk between actuators. We implement this in a visible spectrum photonic integrated circuit platform that satisfies additional requirements of electro-optic modulation, low loss, and manufacturability in a 200 mm foundry process. We use our device to explore the strain response of the newly discovered tin vacancy, and measure frequency tuning and control bandwidth above 20 GHz and 2 GHz, respectively.Genevieve Clark
Transceiver Designs Attaining the Entanglement-assisted communications CapacityWe present a sum-frequency-generation based structured transceiver design that attains the log(1/N_S) scaling promised by the ultimate entanglement-assisted capacity in the low signal brightness (N_S), high noise and high loss regime.Ali Cox
Photonic resource state generation from a minimal number of quantum emittersMulti-photon graph states are a fundamental resource in quantum communication networks, distributed quantum computing, and sensing. These states can in principle be created deterministically from quantum emitters such as optically active quantum dots or defects, atomic systems, or superconducting qubits. However, finding efficient schemes to produce such states has been a long-standing challenge. Here, we present an algorithm that, given a desired multi-photon graph state, determines the minimum number of quantum emitters and precise operation sequences that can produce it. The algorithm itself and the resulting operation sequence both scale polynomially in the size of the photonic graph state, allowing one to obtain efficient schemes to generate graph states containing hundreds or thousands of photons.Bikun Li
Estimating Noise in the Quantum Internet with Quantum Network TomographyThe fragile nature of quantum information makes it practically impossible to completely isolate a quantum state from noise under quantum channel transmissions. Quantum networks are complex systems formed by the interconnection of quantum processing devices through quantum channels. In this context, characterizing how channels introduce noise in transmitted quantum states is of paramount importance. Precise descriptions of the error distributions introduced by non-unitary quantum channels can inform quantum error correction protocols to tailor operations for the particular error model. In addition, characterizing such errors by monitoring the network with end-to-end measurements enables end-nodes to infer the status of network links. In this work, we address the end-to-end characterization of quantum channels in a quantum network by introducing the problem of Quantum Network Tomography. The solution for this problem is an estimator for parameters that define a Kraus decomposition for all quantum channels in the network, using measurements performed exclusively in the end-nodes. We study this problem in detail for the case of arbitrary star quantum networks with quantum channels described by a single Pauli operator, like bit-flip quantum channels. We provide solutions for such networks with polynomial sample complexity. Our solutions provide evidence that pre-shared entanglement brings advantages for estimation in terms of the identifiability of parameters.Matheus Guedes de Andrade
All-photonic multiplexed quantum repeaters based on concatenated bosonic and discrete-variable quantum codesLong distance quantum communication will require the use of quantum repeaters to overcome the exponential attenuation of signal with distance. One class of such repeaters utilizes quantum error correction to overcome losses in the communication channel. Here we propose a novel strategy of using the bosonic Gottesman-Kitaev-Preskill (GKP) code in a two-way repeater architecture with multiplexing. The crucial feature of the GKP code that we make use of, is the fact that GKP qubits easily admit deterministic two-qubit gates, hence allowing for multiplexing without the need for generating large cluster states as required in previous all-photonic architectures based on discrete variable codes. Moreover, alleviating the need for such clique-clusters entails that we are no longer limited to extraction of at most one end-to-end entangled pair from a single protocol run. In fact, thanks to the availability of the analog information generated during the measurements of the GKP qubits, we can design better entanglement swapping procedures in which we connect links based on their estimated quality. This enables us to use all the multiplexed links so that large number of links from a single protocol run can contribute to the generation of the end-to-end entanglement. We find that our architecture allows for high-rate end-to-end entanglement generation and is resilient to imperfections arising from finite squeezing in the GKP state preparation and homodyne detection inefficiency.Filip Rozpedek
Quantum Communication Research in IrelandIreland has a long history of innovation and research in communication systems and photonics most recently led by the SFI CONNECT Research Centre for Future Networks and Communications and Tyndall National Institute. Research on quantum communication systems is rapidly expanding with the recent announcement of a national quantum staging network, IrelandQCI and the centre to centre US-Ireland program between CONNECT, CQN, and QTeQ. This poster provides details of the growing quantum communications ecosystem in Ireland.Dan Kilper
Quantum-enhanced Transmittance sensingWe consider the problem of estimating unknown transmittance of a target bathed in thermal background light. As quantum estimation theory yields the fundamental limits, we employ lossy thermal noise bosonic channel model, which describes sensor-target interaction quantum-mechanically in many practical active-illumination systems (e.g., using emissions at optical, microwave, or radio frequencies). We prove that quantum illumination using two-mode squeezed vacuum (TMSV) states asymptotically achieves minimal quantum Cramér-Rao bound (CRB) over all quantum states (not necessarily Gaussian) in the limit of small input photon number.  We characterize the optimal receiver structure for TMSV input and show its advantage over other receivers using both analysis and Monte Carlo simulation.Zihao Gong
TBDTBDAllison Rubenok
Towards Dynamic Atomic MirrorsWe propose the use of spatially periodic spectral hole burning in Praseodymium (Pr3+) doped in Yittrium Silicate (Y2SiO5) to create a narrowband reflective Bragg grating. This is followed by a strong control pulse to effect electromagnetically induced transparency (EIT) to optically turn the mirror transparent in microseconds, thereby creating an all-optical switch. Such a switch can be used to create dynamical cavities and reconfigurable quantum systems. We are interested in analyzing the behavior of quantized electromagnetic fields in the presence of time-varying boundaries in general. We are developing a time-varying Huttner-Barnett model to analyze dynamic dielectrics.Ashwith Varadaraj Prabhu
Zero Added Loss Entangled Photon Multiplexing for Ground and Space based  Quantum NetworksWe propose a scheme for optical entanglement distribution in quantum networks based on a quasi-deterministic entangled photon pair source. By combining heralded photonic Bell pair generation with spectral mode conversion to interface with quantum memories, the scheme eliminates switching losses due to multiplexing in the source. We analyze this `zero-added-loss multiplexing’ (ZALM) Bell pair source for the particularly challenging problem of long-baseline entanglement distribution via satellites and ground-based memories, where it unlocks additional advantages: (i) the substantially higher channel efficiency \eta of downlinks vs. uplinks with realistic adaptive optics, and (ii) photon loss occurring before interaction with the quantum memory – i.e., Alice and Bob receiving rather than transmitting – improve entanglement generation rate scaling by O(\sqrt{\eta}) Based on numerical analyses, we estimate our protocol to achieve >10 ebit/s at memory multiplexing of 100 spin qubits for ground distance >100 km, with the spin-spin Bell state fidelity exceeding 99%. Our architecture presents a blueprint for realizing global-scale quantum networks in the near-term.Prajit Dhara