Overview: The 2023 SIPQNP featured four topical sessions on all-photonic quantum computing, quantum photonics foundries, entanglement assisted sensing and programmable mode transformations for imaging and computing. Each session comprised of overview talks, a series of idea flash talks, followed by an interactive moderated technical exchange.

Program committee: Sophia Economou, Mercedes Gimeno-Segovia, Zheshen Zhang, Ryan Camacho, Michael Raymer, Matt Eichenfield, Saikat Guha

Participants: Matt Eichenfield, Saikat Guha, Ryan Camacho, Mercedes Gimeno-Segovia, Sophia Economou, Rafael Alexander, Connor Hart, Ulrik Andersen, Dalziel Wilson, Brian Smith, Amit Ashok, Hayden McGuinness, Zac Dutton, Stuart Masson, Anthony Brady, Leo Hollberg, Chris Sparrow, Michael Grace, Paul Juodawlkis, Stephen Ralph, Volker Sorger, Shuo Sun, Dan Blumenthal, Ashlesha Patil, Bikun Li, Nicolas Treps, Derya Cansever, Yong Meng Sua, Elizabeth Goldschmidt, Wenji Wu, Dileep Reddy, Lukasz Komza, Joseph Lukens, Genevieve Clark, Stefan Krastanov, Alp Sipahigil, RuoDing Li, Brendan Shields, Timothy Burt, Clark Embleton, Amy Soudachanh, Mark Meisner, Fengyan Yang, Hakan Turechi, Prateek Mantri, Ali Cox, Tahereh Rezaei, Matheus Guedes de Andrade, Filip Rozpedek, Alex Wendt, Paul Poalkos, Benjamin Szamosfalvi, William Clark, Panagiotis Promponas, Edwin Barnes, Wenhua He, Kanu Sinha, Yuxuan Xue, Dan Kilper, Debayan Bandyopadhyay, Mak Kirkman-Davis, Ashwith Varadaraj Prabhu, Prajit Dhara, Zihao Gong, Allison Rubenok, Aqil Sajjad, Boulat Bash, Roberto Diener, Eneet Kaur, Jane Bambauer, Itay Ozer, Narayanan Rengaswamy, Nithin Raveendran, Emily Van Milligen, Jack Postlewaite, Noel Wan, Mehmet Akbulut

Agenda:

Sunday, February 12

7pm Welcome dinner and poster session

Monday, February 13

7am Breakfast

8am Session 1 All-photonic quantum computing [Chairs: Mercedes Gimeno-Segovia and Sophia Economou]

Goal of the session: This session aims at discussing a few techniques and technologies whose fruition may lead to disruptive / dramatic improvements to the scalability and realizability of fault-tolerant all-photonic quantum computing. Example topics will include: (1) photonic cluster state generation using atomic emitters for discrete variable quantum computing, (2) deterministic preparation of GKP qubits for continuous variable photonic quantum computing, (3) high-speed loss-tolerant electro-optic feedforward in photonic integrated circuits, and (4) energy-efficient cryo-electronic processing for Boolean logic in integrated photonics.

The session will be organized as follows:

8:00am-8:30am Overview talk 1: Chris Sparrow, PsiQuantum

8:30am-9:00am Overview talk 2: Rafael Alexander, Xanadu

9:00am-10:00am Flash talks on enabling technologies

• Alp Sipahigil, UC Berkeley
• Ed Barnes, Virginia Tech
• Bikun Li, University of Chicago
• Shuo Sun, University of Colorado Boulder
• Ashlesha Patil, University of Arizona

10:00am-10:30am Coffee Break

10:30am-noon Moderated Discussion

noon-1 Outdoor Lunch at the Biosphere Patio

1pm Session 2 Quantum Photonics Foundries: Builders and Users [Chairs: Matt Eichenfeld and Ryan Camacho]

Goal of the session: This session seeks to address the following question: what foundry capabilities exist to support quantum photonics and how can future users take advantage of these capabilities? The session will consist of two primary sets of speakers, each of whom will give short “flash” talks:

1pm-1:45pm Talks from Leading experts representing various foundries and material platforms that are or may be able to support the infrastructure needs of quantum photonics and applications areas

• Paul Juodawlkis, MIT Lincoln Laboratories
• Hakan Tureci, Princeton University
• Matt Eichenfield, University of Arizona

1:45pm-2:30pm Talks from Users of foundry platforms for quantum experiments

• Dan Blumenthal, UC Santa Barbara
• Stephen Ralph, Georgia Institute of Technology
• Volker Sorger, George Washington University
• Noel Wan, QuERA Computing
• Shuo Sun, University of Colorado Boulder
• Gen Clark, MITRE

2:30pm-3:00pm Coffee Break

3:00pm-4:30pm Moderated discussion/panel on transformational technologies for quantum photonics in scalable processes and how to get foundries to manufacture these technologies if they are not already available.

4:30pm-5:30pm Free Time

5pm-6pm Poster Session

6pm-7pm Keynote dinner-time talk by Prof. Nasser Peyghambarian, University of Arizona

7pm Dinner

7am Breakfast

8 am Session 3 Individual and Distributed entanglement assisted sensing [Organizers: Mike Raymer and Zheshen Zhang].

Session chairs: Elizabeth Goldschmidt and Brian Smith

Goal of the session: The fundamental limits of precision in estimating parameters embedded in light or matter are ultimately governed by the laws of quantum mechanics. This session aims at surveying how to quantify these quantum performance limits, and discussing promising avenues of significant quantum enhancements in sensor performance, both for individual quantum-enhanced sensors as well as a collection of distributed sensors—equipped with entanglement—working toward a collective estimation task. The talks in this session will involve sensors that use non-classical photonic illumination schemes, preparation of collective entangled states of atomic sensors, design of non-classical optical receivers, and more, which if realized, could lead to dramatic improvements in sensing performance with applications ranging magnetometry, accelerometry, gravimetry, radio-frequency photonic sensors, dark matter detection, navigation, astronomical imaging, and more. The session will begin with two overview talks, followed by flash talks and a moderated discussion at the end.

8am-8:20am Overview talk 1 [Individual sensors] Ronald Walsworth, University of Maryland

8:20am-8:45am Flash talks [applications of standalone quantum sensors] ~8 minutes per talk

• Stuart Masson, Columbia University
• Hayden McGuinness, Sandia National Laboratory
• Leo Hollberg, Stanford University

8:45am-9:15am Panel discussion: standalone sensors

9:15am-9:45am Break

9:45am-10:05am Overview talk 2 [Distributed sensors] Ulrik Andersen, DTU

10:05am-10:25am Flash talks [applications of quantum sensor networks] ~8 minutes per talk

• Dalziel Wilson, University of Arizona
• Anthony Brady, University of Southern California

10:25am-10:55am Panel discussion: distributed sensors

10:55am-11:15am Break 11:15am-noon Joint moderated discussion

noon-1 Outdoor Lunch at the Biosphere Patio

1 pm Session 4 Programmable mode transformations for imaging and computing [Chair: Saikat Guha]

Goal of the session: The goal of this session is to scope out the state of the art and development needs for optical-domain multi-spatial-temporal-spectral mode programmable linear transformations to support disruptive improvements in capabilities in receivers for passive imaging in the sub-Rayleigh regime, receiver designs for active sensors, and potentially for photonic quantum computing.

Applications of programmable mode sorters

1:00pm-1:20pm Applications of mode sorters to passive imaging, Amit Ashok, University of Arizona

1:20pm-1:40pm Applications of multiplane light conversion (MPLC) mode sorters to quantum parameter estimation, Nicolas Treps, Sorbonne University

1:40pm-2:00pm Applications of mode sorters to quantum sensing and quantum computing, Michael R. Grace, Raytheon BBN Technologies

2:00pm-2:40pm Moderated discussion on applications of mode sorting to photonic quantum information processing

2:40pm-3:00pm Coffee Break

Experimental realizations of mode sorters

3:00pm-3:20pm Programmable temporal mode sorters, Brian Smith [spectral mode sorters], University of Oregon

3:20pm-3:40pm Programmable spectral mode sorters, Joe Lukens [temporal mode sorters], Arizona State University

3:40pm-4:20pm Moderated Discussion on scalable design of programmable mode sorters for space, time and/or frequency modes

4:20pm-4:30pm Program Committee Members: Concluding remarks

4:30pm Adjourn 5pm Arranged transportation to Tucson (Downtown, UArizona campus, and TUS airport)

Posters

1. Integrated quantum photonics with artificial atoms in silicon || Lukasz Komza

Silicon 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.

2. Frequency-Bin Encoding for Quantum Networking || Joseph Lukens

Frequency-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.

3. Piezoelectric control of spin quantum memories in a cryogenic programmable photonic circuit platform || Genevieve Clark

Group-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.

4. Transceiver Designs Attaining the Entanglement-assisted communications Capacity || Ali Cox

We 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.

5. Photonic resource state generation from a minimal number of quantum emitters || Bikun Li

Multi-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.

6. Estimating Noise in the Quantum Internet with Quantum Network Tomography || Matheus Guedes de Andrade

The 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.

7. All-photonic multiplexed quantum repeaters based on concatenated bosonic and discrete-variable quantum codes || Filip Rozpedek

Long 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.

8. Quantum Communication Research in Ireland || Dan Kilper

Ireland 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.

9. Quantum-enhanced Transmittance sensing || Zihao Gong

We 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.

10. Towards Dynamic Atomic Mirrors || Ashwith Varadaraj Prabhu

We 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.

11. Zero Added Loss Entangled Photon Multiplexing for Ground and Space based Quantum Networks || Prajit Dhara

We 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.

12. A Quantum-network test-bed over deployed fiber at Berkeley || Wenji Wu

Quantum networks enable the transmission of information in the form of quantum bits (qubits) between physically separate quantum nodes. Based on laws of quantum mechanics, such as superposition, entanglement, quantum measurement, and the no-cloning theorem, quantum networks are envisioned to achieve novel capabilities that are provably impossible using classical networks and could be transformative to science, economy, and national security. These novel capabilities range from cryptography, sensing and metrology, distributed systems, to secure quantum cloud computing. Today, quantum networks are in their infancy. Like the Internet, quantum networks are expected to undergo different stages of research and development until they reach a level of practical functionality. Quantum network technologies are currently in development with many promising R&D efforts underway.

DOE/ASCR is funding Berkeley Lab, UC Berkeley, Caltech, and University of Innsbruck on the QUANT-NET project. The goal of the project is to build a three-node distributed quantum computing testbed between two sites, LBNL and UC Berkeley (UCB) connected with an entanglement swapping substrate over optical fiber and managed by a quantum network protocol stack. The QUANT-NET research team (we) plan to demonstrate entanglement between small-scale ion trap quantum processors at both locations. On top of this capability, we will implement the most basic building block of distributed quantum computing by teleporting a controlled-NOT gate between two nodes. The QUANT-NET project is being carried out according to the plan. Significant progress has been made in designing and implementing the quantum testbed infrastructure, developing the ion trap quantum processors, building single color-centers in silicon nano-photonics, and designing the quantum network architecture and protocol stack. In this poster presentation, we will showcase the QUANT-NET project’s objective, key technologies, and design. In addition, we will share our insights on some challenges we encountered within the project development process and reflect on some lessons learned.