**Monday, October 2, 2017
Lazaridis QNC 0101**

8:30 am | Registration |

9:00 am | Opening remarks by IQC Director Kevin Resch |

9:10 am | Crystal Senko, Institute for Quantum Computing Plenary talk: Ion traps and multi-level quantum systems |

10:10 am | Shantanu Debnath, University of California, Berkeley A Programmable Quantum Computer Using Trapped Atomic Ions |

10:55 am | Break |

11:15 am | Kristi Beck, Joint Quantum Institute Booting up a Universal Ion-trap Quantum Computing System |

12:00 pm | Jordi Tura, MPQ Germany Quantum algorithms tailored to small quantum computers |

12:45 pm | Lunch |

1:30 pm | Career panel discussion |

2:30 pm | Break |

3:00 pm | Amir Safavi-Naeini, Stanford University Plenary talk: Photons and Phonons for Classical and Quantum Nanotechnologies |

4:00 pm | Angela Kou, Yale University Building quantum materials with superconducting circuits (PDF) |

5:00 pm | Reception |

**Tuesday, October 3, 2017
Research Advancement Centre (RAC) Room 2009**

9:00 am | Lea Santos, Yeshiva University Plenary talk: Nonequilibrium dynamics of many-body quantum systems |

10:00 am | Monica Allen, Stanford University Visualization of chiral edge states in a magnetic topological insulator |

10:45 am | Break |

11:05 am | Javier Sanchez-Yamagishi, Harvard University Probing magnetic noise from currents and spins in 2d layered materials using diamond NV centers |

11:50 am | Renate Landig, Harvard University Observation of discrete time-crystalline order in black diamond |

12:35 pm | Lunch |

1:30 pm | Marina Radulaski, Stanford University Color Center Quantum Photonics |

2:15 pm | Alp Sipahigil, Harvard University An integrated diamond nanophotonics platform for quantum optical networks |

3:00 pm | Break |

3:15 pm |
Arash Ahmadi, Institute for Quantum Computing |

4:00 pm | RAC 1 lab tours |

5:00 pm | RAC 2 lab tours |

6:00 pm | Dinner at RAC 2 |

**Wednesday, October 4, 2017
Lazaridis QNC 0101**

9:00 am | Irina Novikova, College of William and Mary Plenary talk: Cool quantum optics with hot atoms |

10:00 am | Akihisa Goban, University of Colorado A Fermi-degenerate three-dimensional optical lattice clock |

10:45 am | Break |

11:05 am | Ana Asenjo-Garcia, California Institute of Technology Selective radiance: a new paradigm for enhancing atom-light interactions and improving quantum memories |

11:50 am | Monika Aidelsburger, Ludwig-Maximilian University of Munich Floquet engineering with interacting ultracold atoms |

12:35 pm | Lunch |

1:30 pm | Victor Albert, California Institute of Technology Performance of single-mode bosonic codes (PDF) |

2:15 pm |
Joseph Lukens, Oak Ridge National Laboratory |

3:00 pm | Break |

3:15 pm | Anja Metelmann, Princeton University Nonreciprocal Interactions and Devices via Reservoir Engineering |

4:00 pm | Lazaridis QNC lab tours |

6:30 pm | Banquet dinner at the University Club |

**Thursday, October 5, 2017****Lazaridis QNC 0101**

9:00 am | Daniel Oblak, University of Calgary Building quantum networks |

9:45 am | Michael Kues, INRS Canada On-chip generation of multi-photon and high-dimensional entangled quantum states and their coherent control |

10:30 am | Break |

10:50 am | Robert Stockill, University of Cambridge Optical Networks of Quantum Dot Spins (PDF) |

11:35 am | Klaus D. Jöns, KTH Sweden On-chip hybrid quantum circuits |

12:20 pm | Closing remarks by Raymond Laflamme |

12:30 pm | Lunch |

## Abstracts

**Crystal Senko, Institute for Quantum Computing**

Plenary talk: Ion traps and multi-level quantum systems

I give an overview of trapped ion quantum information and discuss prospects for implementing multi-valued quantum logic using trapped ions. Qudits (the multi-state generalization of qubits) are attractive for quantum computing because they enable a much larger Hilbert space for the same number of trapped ions, which may allow us to improve the information capacity of a quantum processor. I describe possible advantages and disadvantages of using qudits in place of qubits, and lay out the protocols that my lab will test for implementing measurements, single-qudit operations, and two-qudit operations in a trapped ion system.

**Amir Safavi-Naeini, Stanford University**

Plenary talk: Photons and Phonons for Classical and Quantum Nanotechnologies

In this talk I'll outline our work on controlling photons and phonons on a chip. Both optical and mechanical devices are ubiquitous in classical technologies. Combining both on a chip and studying their interactions enables new technologies in both the classical and quantum domain. In this talk, I'll outline our work in this direction.

**Shantanu**** Debnath, University of California, Berkeley**

A Programmable Quantum Computer Using Trapped Atomic Ions

Experimental realizations of small quantum computers have so far been achieved by engineering systems specifically to meet the requirements of particular algorithms. Here, we present a quantum processor based on trapped ions that allows a user to program any quantum algorithm in the software while staying blind to the underlying hardware [1]. The system consists of linear chain of trapped Ytterbium ions that are coherently manipulated at the single qubit level using an array of optical addressing Raman beams. By using the collective vibrations of the chain, long range entangling interactions are engineered such that a fully connected graph of two-qubit native gates is realized. We describe the implementation of a basic quantum computation architecture where programmed algorithm sequences are decomposed into native gate operations effected by shaped laser pulses. This is demonstrated as we implement several algorithms that are based on the quantum Fourier transform, the Grover search and the fault-tolerant encoding of a logical qubit. Additionally we extend the application of the processor in the quantum simulation of a Hubbard like system of bosons represented by the local vibrational (phonon) modes of individual ions in a chain. By spatially and spectrally accessing these modes we study the hopping of phonons between ions and suppression thereof on applying programmable local blockades on each site.

[1] S. Debnath, N. M. Linke, C. Figgatt, K. A. Landsman, K. Wright, and C. Monroe Nature 536, 63 (2016).

**Kristi Beck, Joint Quantum Institute**

Booting up a Universal Ion-trap Quantum Computing System

Trapped ions provide a promising platform for quantum computation, with fully connected graphs of two-qubit gates and fidelities exceeding 99% [1]. After giving an overview of the system architecture, I will present the design and implementation of a new room-temperature surface-electrode-trap universal quantum computing system that is being constructed at the University of Maryland to realize an error-corrected logical qubit. The system traps a chain of laser-cooled 171Yb+ ions, which are laser cooled to their motional ground state and whose hyperfine state serves as our physical qubit. The optical design enables individual addressing of up to 32 such qubits using Raman transitions driven by counter-propagating pulses of 355-nm light and read out either as a group or individually by a beam of 369-nm light.

This work is supported by the Intelligence Advanced Research Projects Activity (IARPA) LogiQ Program through the U.S. Army Research Office.

[1] N. M. Linke et al., Proc. Natl. Acad. Sci. 114, 13 (2017)

**Jordi Tura, MPQ Germany**

Quantum algorithms tailored to small quantum computers

Quantum computers are expected to have a deep impact in the simulation of quantum systems. Of particular interest is the ability to study their ground states, which are classically often intractable. On the one hand, they encode relevant physical properties of the system and, on the other hand, many optimization problems can be mapped to finding the ground state of a Hamiltonian.

In the first part of the talk, I will present a series of new quantum algorithms inspired by the classical power iteration method. The algorithm prepares a good approximation of the ground state using techniques which were recently developed in the context of QLSP (Quantum Linear Systems Problem) solvers for implementing operators that have suitable Fourier or Chebyshev representations. Contrary to algorithms based on adiabatic evolution or naïve phase estimation, this algorithm provides a certification of success. Its runtime is quadratically better than the naïve phase estimation method and polynomial in the classical iteration length, with small memory requirements, making it an attractive candidate for potential applications of small quantum computers.

In the second part of the talk, I will present a greedy method to prepare low energy states of local Hamiltonians in a quantum computer that can support a very limited number of operations without losing coherence (i.e., a first-generation quantum computer, still unable to handle quantum error correction). The method shows numerically good performance for systems of tens to hundreds of qubits. This has been benchmarked in systems such that their ground state can be computed efficiently; namely (i) local 1D spin systems, using tensor networks and DMRG and (ii) quadratic fermion systems, using the Jordan-Wigner transformation.

Joint work with Yimin Ge and Juan Ignacio Cirac.

**Lea Santos, Yeshiva University**

Plenary talk: Nonequilibrium dynamics of many-body quantum systems

Advances in quantum information science and many-body quantum physics have been intertwined. One needs quantum computers to accurately simulate many-body quantum systems. At the same time, quantum computers are many-body quantum systems, so a good understanding of the latter is necessary for the development of the first. In this talk, I will discuss our efforts to describe the dynamics of many-body quantum systems from the moment the systems are taken out of equilibrium to the moment they reach a new equilibrium point. We unveil different behaviors at different time scales and show how information about the spectrum of a many-body quantum system can be extracted by the sole analysis of its time evolution.

**Monica Allen, Stanford University**

Visualization of chiral edge states in a magnetic topological insulator

Topological insulators with ferromagnetic ordering exhibit the quantum anomalous Hall effect, in which a chiral one-dimensional edge state encloses an insulating interior. We provide a real-space visualization of the local conductivity profile in Cr modulation doped (Bi,Sb)2Te3 using microwave impedance microscopy (MIM). Well-defined edge states appear in the quantum anomalous Hall regime, which is robust at magnetic fields exceeding the coercive field. Our images reveal a dramatic change in the edge state pattern and microwave response near the topological phase transition between the Chern number N=1 and N=0 states. By mapping the non-monotonic evolution of the local complex microwave response in magnetic field, we construct a phase diagram of competing topological states and unveil the microscopic nature of dissipation and conductivity in each regime.

**Julia Mundy, University of California, Berkeley**

Tuning Magnetic Frustration in Oxide Superlattices

Materials systems with many strongly interacting degrees of freedom can host some of the most exotic physical states known. In thin films, the interface between two distinctquantum materials forms a further playground to engineer emergent ground states. Specifically—and in contrast to bulk crystals—such an abrupt heterointerface can utilize the broken symmetry/reduced dimensionality inherent to the interface as well as induce chemical potential offsets, epitaxial strain and provide proximity to functional phases. This not only creates a platform to change the materials properties, but more profoundly directly modifies the quantum many body interactions underpinning the physical ground state.

In this talk, I will discuss our work synthesizing thin films and superlattices of metastable hexagonal oxides. Such hexagonal materials can have properties that differ from their more widely studied cubic counterparts due to the strong spin frustration intrinsic to the trigonal lattice. This spin frustration can lead to a number of different magnetic states, including the canonical quantum spin liquid. Here, I will present our work studying the magnetic ordering in these films using a combination of neutron scattering, bulk magnetometery and x-ray based probes. I will also demonstrate how we can perturb the lattice at the sub-Angstrom scale using a superlattice architecture to controllably themagnetic frustration.

**Renate Landig, Harvard University**

Observation of discrete time-crystalline order in black diamond

The interplay between periodic driving, disorder and strong interactions has been predicted to result in exotic `time-crystalline phases, in which a system exhibits temporal correlations at integer multiples of the fundamental driving period, breaking the discrete time-translational symmetry of the underlying drive. In this talk, we report the experimental observation of such discrete time-crystalline order in a driven, disordered ensemble of about one million dipolar spin impurities in diamond at room temperature. We observe long-lived temporal correlations, experimentally identify the phase boundary and nd that the temporal order is protected by strong interactions. This order is remarkably stable to perturbations, even in the presence of slow thermalization. Our work opens the door to exploring dynamical phases of matter and controlling interacting, disordered many-body systems.

**Javier Sanchez-Yamagishi, Harvard University**

Probing magnetic noise from currents and spins in 2d layered materials using diamond NV centers

Diamond NV centers are ultra-sensitive magnetometers which operate from room to cryogenic temperatures. By placing nanoscale samples directly on a diamond surface with shallow implanted NV centers it is possible to measure magnetic signals which are too small to observe with traditional probes. I will discuss our recent work using NV centers to measure local magnetic noise emanating from spins and electrical currents in 2d layered materials. By fabricating high-quality graphene devices on a diamond substrate, we can measure the magnetic noise due to thermal fluctuations in the graphene electron sea and, in turn, probe the local structure of the electrical conductivity. I will discuss how this measurement technique can be used to study new electronic behaviors in the ballistic, diffusive and hydrodynamic transport regimes.

**Marina Radulaski, Stanford University**

Color Center Quantum Photonics

Color centers are solid-state quantum emitters with excellent optical and spin coherence properties that have been crucial to the successful line of research on NV centers in diamond. The new generation of color centers, which includes the silicon-vacancy center in diamond and silicon carbide color centers, offers properties beneficial for quantum communication, computing and metrology.

In this talk, I will introduce a roadmap to solid-state multi-emitter cavity QED demonstrations with applications in nonclassical light generation and optical switching. This includes a theoretical discovery of a new single-photon generating mechanism called the subradiant photon blockade. Next, I will discuss our experimental progress on achieving strong light-matter interactions with silicon carbide and diamond color centers. Finally, I will present a scalable quantum photonics platform implemented in a commercial wafer of silicon carbide featuring an array of room temperature qubits.

**Alp Sipahigil, Harvard University**

An integrated diamond nanophotonics platform for quantum optical networks

Solid-state quantum-emitters with long spin coherence times and strong interactions with single-photons can form the building blocks of a quantum network. To date, no solid-state quantum-emitter has yet been able to satisfy both of these requirements simultaneously. In this talk, I will discuss experiments which demonstrate that silicon-vacancy (SiV) color centers in diamond can address both of these challenges. First, we integrate SiV centers into diamond nanophotonic devices to obtain strong light-matter interactions. Using this platform, we demonstrate a quantum optical switch controlled by a single SiV center and entanglement generation between two SiVs in a single nanophotonic device. By cooling SiVs down to 100mK, we improve the SiV spin coherence time by five orders of magnitude and achieve a coherence time of 13-milliseconds. These results make SiV centers in nanophotonic devices a leading solid-state platform for quantum networks.

**Irina Novikova, College of William and Mary**

Plenary talk: Cool quantum optics with hot atoms

Interactions between light and atoms provided an unprecedented range of tools for controlling quantum state of both photons and atoms. In this talk I will discuss a possible pathways for generation of non-classical optical fields by means of resonant interaction with Rb vapor, and the potential

applications for enhancing the measurement sensitivity beyond the shot noise limit.

**Akihisa Goban, University of Colorado**

A Fermi-degenerate three-dimensional optical lattice clock

The pursuit of better atomic clocks has advanced many research areas, providing better quantum state control, new insights in quantum science, tighter limits on fundamental constant variation, and improved tests of relativity. In our previous 1D optical lattice, atomic interactions cause suppression and broadening of the atomic resonance, limiting the clock stability [1]. To overcome this limitation, we demonstrate a scalable solution which takes advantage of the high, correlated density of a degenerate Fermi gas in a three-dimensional optical lattice to protect against on-site interaction shifts. Using a state-of-the-art ultra-stable laser, we achieve an unprecedented level of atom-light coherence, reaching a quality factor Q=5.2*10^15 with 10^4 atoms. Finally, we take advantage of the large atom number and long coherence time in this system by performing a synchronous clock comparison between two regions of the 3D lattice, yielding a 5×10^(-19) measurement precision in 1 hour [2].

References

[1] T. Nicholson et al., Nature communications 6 6896 (2015).

[2] S. L. Campbell, R. B. Hutson et al., arXiv: 1702.01210 (2017).

**Ana Asenjo-Garcia, California Institute of Technology**

Selective radiance: a new paradigm for enhancing atom-light interactions and improving quantum memories

Spontaneous emission, in which photons are scattered into undesired channels, limits how strongly atoms interact with preferred photonic modes. Typically, it is assumed that this scattering occurs at a rate given by a single isolated atom, which in turn gives rise to standard limits of fidelity in applications such as photonic quantum memories and quantum gates. However, this assumption is invalid when atoms are close enough to each other so that they give rise to collective subradiant states, whose free-space decay is suppressed. Inspired by subradiance, we introduce the concept of “selective radiance”. Whereas subradiant states experience a reduced coupling to all optical modes, selectively-radiant states radiate efficiently into a desired channel and very inefficiently into undesired ones. These states, which naturally appear in chains of atoms coupled to nanophotonic structures, allow for a photon storage error that performs exponentially better with number of atoms than previously known bounds.

A. Asenjo-Garcia et al., http://arxiv.org/abs/1703.03382

**Monika Aidelsburger, Ludwig-Maximilian University of Munich**

Floquet engineering with interacting ultracold atoms

Floquet engineering is an important tool for the engineering of novel band structures with interesting properties that go beyond those offered by static systems. Recently, Floquet systems have enabled the generation of Bloch bands with non-trivial topological properties, such as the Hofstadter and Haldane model. This led to the observation of chiral Meissner currents and the first Chern-number measurement with charge-neutral atoms.

Besides this success studies of many-body phases in driven systems remains experimentally challenging in particular due to the interplay between periodic drivingan interactions. In a driven system energy is not conserved which can lead to severe heating. In order to find stable parameter regimes for the generation of driven many bodyphases it is essential to develop a deeper understanding of the underlying processes.

Here, I briefly review recent experimental advances in the generation of topological band structures in the non-interacting regime using Floquet engineering and present first studies of interacting atoms in driven 1D lattices.

**Peter McMahon, Stanford University**

Computing using networks of optical parametric oscillators

Combinatorial optimization problems, including many nondeterministic polynomial-time–hard (NP-hard) problems, are central in numerous important application areas, including operations and scheduling, drug discovery, finance, circuit design, sensing, and manufacturing. Despite large advances in both algorithms and digital computer technology, even typical instances of NP-hard problems that arise in practice may be very difficult to solve on conventional computers. There is a long history of attempts to find alternatives to current von Neumann–computer–based methods for solving such problems, including use of neural networks realized with analog electronic circuits and by using molecular computing. A major topic of contemporary interest is the study of adiabatic quantum computation (AQC) and quantum annealing (QA). Sophisticated AQC/QA devices are already under study, but providing dense connectivity between qubits remains a major challenge, with important implications for the efficiency of AQC/QA systems.

Networks of coupled optical parametric oscillators (OPOs) are an alternative physical system, with an unconventional operating mechanism, for solving the Ising problem and by extension many other combinatorial optimization problems. We have realized a fully-programmable 100-spin Ising machine using a network of OPOs, and with it can solve many different Ising problems. In cases in which exact solutions are not easy to obtain, we can find good approximate solutions. Our design supports all-to-all connectivity among the implemented spins via a combination of time-division multiplexing and measurement feedback.

In this talk I will describe our work on constructing Ising machines using OPO networks with feedback, and will present the experimental results from our first prototype system.

[1] P.L. McMahon, et al. Science 354, 6312, pp. 614-617 (2016).

**Anja Metelmann, Princeton University**

Nonreciprocal Interactions and Devices via Reservoir Engineering

An interaction process between two quantum systems is in general reciprocal. This means that forward and backward process are inherently present and both systems are influenced by the interaction. One may ask the question if it is possible to break this symmetry, i.e., if one can realize a unidirectional interaction between two quantum systems? This is indeed possible, as we found that any factorisable (coherent) Hamiltonian interaction can be rendered directional if balanced with the corresponding dissipative interaction. This powerful concept can be exploited to engineer nonreciprocal devices for quantum information processing, computation and communication protocols, e.g., to achieve control over the direction of propagation of photonic signals, enabling to construct circulators, optical

isolators or directional ampli ers. In this talk I will introduce the basic concept and discuss possible implementations for nonreciprocal devices in superconducting circuit and optomechanical architectures.

**Joseph Lukens, Oak Ridge National Laboratory**

Classical Telecom Meets Spectral Qubits: Frequency-Bin Encoding for Photonic Quantum Information

Photons have proven to be workhorses in both classical optical communications and quantum information. Nevertheless, the two fields have often operated independently of each other, with the technological developments in one community passing by largely unnoticed in the other. One example lies in the adoption of advanced modulation and control techniques for time and frequency in classical fiber optics–degrees of freedom of particular value for their robustness and exibility. Only fairly recently have quantum elds begun to receive their deserved attention in the context of full-edged frequency-based quantum information processing, and there appears to be a wealth of potential for such states in future quantum networks.

In this talk, I will discuss our recent work on one subset of time- frequency quantum information: frequency-bin encoding. Beginning with experiments demonstrating intricate control of the spectro-temporal

properties of single- and two-photon states, I will introduce our paradigm

for universal quantum computation based on spectral qubits, pulse shapers, and electro-optic modulators|in turn discussing opportunities for scalable networks and frequency-multiplexed interconnects. Thereafter, I will relate new experiments developing these quantum gates in the laboratory, concluding with a general outlook of this growing field.

**Daniel Oblak, University of Calgary**

Building quantum networks

Around the globe major funding is being put towards implementing quantum links and networks facilitated by either free-space transmission to and from satellites or through fibre-optic cables. The motivation ranges from expanding the already mature quantumkey-distribution (QKD) application to more ambitious goals of creating a quantuminternet for quantum computers and metrology. In this talk, I will present the work done in our lab to implement the various components and systems needed for realizing quantum networks. This includes Bell-state measurements between photons travelling over deployed optical fibres – co-existing with classical communication – which enables measurement-device-independent QKD and quantum teleportation. Another key element for long-distance quantum communication is the quantum memory required in most quantum repeaters protocols. I will focus on our lab’s quantum memory realizations in rare-earth ion doped solids. This will highlight their benefits such as long coherence times, large multimode storage capacity, and scalability together with the challenge of finding the one ideal system that incorporates all these benefits.

**Michael Kues, INRS Canada**

On-chip generation of multi-photon and high-dimensional entangled quantum states and their coherent control

Complex entangled photon states are essential towards solving questions in fundamental physics and are at the heart of quantum information science. Integrated photonics has become a leading platform for the compact, cost-efficient, and stable generation and processing of optical quantum states. However, current on-chip schemes have been limited to the realization of basic twodimensional (i.e., qubit), two-photon states and ways of accessing and manipulating more complex states without drastically increasing quantum circuit complexity have remained elusive. Here we show that exploiting integrated frequency combs based on high-Q nonlinear microring resonators can provide solutions for scalable complex quantum state generation and can enable practical state control methods. We demonstrate the on-chip generation of multi-photon entangled qubit states, as well as bi-photon entangled high-dimensional (quDit) states, over a broad frequency comb spanning several telecommunications bands. Using off-the-shelf telecommunications components, we introduce a platform for the coherent manipulation of these states.

**Klaus D. Jöns, KTH Sweden**

On-chip hybrid quantum circuits

A. W. Elshaari^{1}, I. Esmaeil Zadeh^{2}, A. Fognini^{2}, D. Dalacu^{3}, P. J. Poole^{3}, M. E. Reimer^{4}, V. Zwiller^{1,2}, and K. D. Jöns^{1*}

^{1}Applied Physics Department, Royal Institute of Technology, Albanova University Centre, Roslagstullsbacken 21, 106 91 Stockholm, Sweden^{2}Kavli Institute of Nanoscience, Delft University of Technology, Lorentzweg 1, 2628CJ Delft, The Netherlands^{3}National Research Council of Canada, Ottawa, K1A 0R6, Canada^{4}Institute for Quantum Computing and Department of Electrical & Computer Engineering, University of Waterloo, Waterloo, N2L 3G1, Canada

Quantum communication applications require a scalable approach to integrate bright sources of entangled photon-pairs in complex on-chip quantum circuits. Currently, the most promising sources are based on III/V semiconductor quantum dots. However, complex photonic circuitry is mainly achieved in silicon photonics due to the tremendous technological challenges in circuit fabrication. We take the best of both worlds by developing a new hybrid on-chip nanofabrication approach [1], allowing to integrate III/V semiconductor nanowire quantum emitters into silicon-based photonics. We demonstrate for the first time on-chip generation, spectral filtering, and routing of single-photons from selected single and multiple nanowire quantum emitters all deterministically integrated in a CMOS compatible silicon nitride photonic circuit [2]. Our new approach eliminates the need for off-chip components, opening up new possibilities for large-scale quantum photonic systems with on-chip single- and entangled-photon sources.

[1] I. Esmaeil Zadeh et al., Nano Letters 16, 2289-2294 (2016).

[2] A. W. Elshaari et al., in press Nat. Commun., see arXiv:1611.03245 (2016).

*Corresponding author: email: klausj@kth.se