**Quantum REU**

NOW ACCEPTING APPLICATIONS!! Anticipated program dates for 2024 are 05/28/24 - 08/2/24.

The priority application deadline is February 15, 2024, although applications will be accepted until March 1, 2024. Click here to apply: reuapply.rice.edu

#### Project listed by Dr. Hanyu Zhu

**Project: **Next-generation electronics and quantum information technology will be supported by nanodevices with strong quantum effects. The operation conditions of such devices include high electric field, large thermal gradient, and possibly cryogenic temperatures. The far-from-equilibrium dynamics of such devices occurs at atomic scale (10^-10 meter) and ultrafast speed (<10^-12 second). To control and probe the device physics with such precision, our research focus on manipulating the structure of van der Waals two-dimensional materials and observe the interaction among quantum electronic, spin, and lattice states in a wide energy range from meV to eV with ultrafast spectroscopy. In this REU/RET project, we will teach undergraduate basic concepts and recent frontiers of non-equilibrium materials physics and optical engineering. We will train undergraduate students to prepare nanomaterials and devices, characterize their basic optical and electrical properties, and package them for studying the energy flow between electrons and atoms with advanced spectroscopy and imaging. In particular, the spin-atom coupling under intense driving fields and high dynamic stress will be investigated with ultrafast time-resolved terahertz and optical spectroscopy at the van der Waals interfaces.

#### Project listed by Dr. Tirthak Patel (tp53@rice.edu) ** **

**Title: "Optimizing Compilation Strategies for Variational Quantum Circuits"**

**Project: **In this REU project, the student will delve into the exciting field of quantum computing by focusing on compilation solutions for variational quantum circuits. Variational quantum circuits play a pivotal role in quantum machine learning and optimization algorithms, where parameterized quantum gates are tuned to minimize a cost function. The student will explore and develop novel compilation strategies to enhance the efficiency and performance of variational quantum circuits. This involves investigating gate synthesis, circuit optimization, architecture-aware representations, and resource-aware compilation techniques to minimize gate count, depth, and overall computational cost. The student will gain hands-on experience with quantum programming language interface, quantum circuit optimization tools, and quantum cloud offerings, contributing to advancing practical quantum computing applications.

Overall, the REU project will provide a unique opportunity for the student to work at the intersection of quantum computing and compilation, gaining valuable insights into the challenges and opportunities within the field. By the end of the project, the student is expected to produce a comprehensive report detailing the developed compilation strategies, their impact on variational quantum circuits, and potential avenues for further research. This project will enhance the student's understanding of quantum computing compilers and contribute to the broader goal of making quantum algorithms more practical and scalable for real-world applications.

#### Project listed by Dr. Guido Pagano (pagano@rice.edu)

**Project: **Laser-cooled atomic ions trapped by electromagnetic fields provide pristine quantum systems that can be engineered from the ground up to an unprecedented level of control. Atoms interacting with lasers offer unmatched coherence properties, deterministic entanglement generation and nearly perfect detection of individual quantum systems. In our lab (http://paganolab.rice.edu) we use trapped ions to assemble atom-by-atom quantum systems whose parameters can be tailored microscopically to investigate unexplored quantum many-body phenomena. In particular, we are interested in gaining control on individual ions to perform local cooling and “shelving” operations to protect quantum information stored in the trapped-ion qubits. The REU fellow will familiarize with a large range of technologies and applications ranging from UHV vacuum systems, laser optical systems, atomic sources, FPGA programming and laser cooling and trapping of atomic ions. Possible projects range from setting the laser infrastructure for shelving laser, to investigating new pathways to prepare Yb+ in a metastable state and to improving the capabilities of our python-based control system.

#### Project listed by Dr. Songtao Chen (songtao.chen@rice.edu)

**Quantum Defects and Photonics (QDP) Lab**

**Context: **Optically interfaced solid-state spins are promising candidates for a variety of quantum technologies including quantum computing and communication. These spin systems have the advantage of storing quantum information locally in individually addressable particles that can be manipulated and controlled coherently using optical and microwave fields. Meanwhile, the spin-entangled single photons can be leveraged to carry and distribute quantum information in a network via optical fibers. To build such a fiber-based quantum networking system, atomic defects with optical transitions in the telecom range, such as single erbium ions [1,2] and single T centers [3,4], are preferred to minimize the fiber transmission loss. In our group (http://chenlab.rice.edu), we utilize single T centers in silicon to construct the quantum network node and repeater devices for building a large-scale quantum network. We develop novel techniques and protocols to manipulate the quantum states of the T-center qubits and engineer interactions between them. On a system level, we aim to build spin-based hybrid integrated silicon quantum photonic chips.

**Project: **One of key tasks in our research is to enhance the light-matter interactions for single T centers in silicon, which is realized by integrating single T centers with low loss, small mode-volume silicon photonic crystal nanocavities. The REU fellow’s research will first focus on the phase-sensitive measurement of the silicon nanophotonic cavity that will be used to couple with single T centers. The REU fellow will actively participate in the design, build-up and characterization of a fiber-based interferometer setup, as well as relevant measurement and data processing to extract cavity reflection profiles. Furthermore, the REU fellow will also participate in analysis of the cavity-enhanced light-matter interaction under the Jaynes-Cummings and Tavis-Cummings framework by using the QuTiP toolbox to solve the Lindblad master equation. This project will train the REU fellow in the techniques of nanophotonic phase-sensitive measurement, laser alignment and stabilization, fiber optics, and fiber-device coupling, as well as general laboratory techniques in computer experimental control and data acquisition. Meanwhile, the project will also train the REU fellow on the theory of cavity quantum electrodynamics and related quantum optical method to control the single T centers inside the cavity.

**References:**

[1] Chen, S. et al., Science 370, 592-595 (2020)

[2] Ourari, S. et al., Nature 620, 977-981 (2023)

[3] Higginbottom, D.B. et al., Nature 607, 266-270 (2022)

[4] Johnston, A. et al., arXiv preprint arXiv:2310.20014 (2023)

#### Project listed by Dr. Shengxi Huang (Shengxi.huang@rice.edu)

**Title: "Single-Photon Emission from Two-Dimensional Materials"
Lab: Rice SCOPE Lab (https://scopelab.rice.edu/)**

**Context: **Single photons, often called flying qubits, have enormous promise to realize scalable quantum technologies ranging from an unhackable communication network to quantum computers. However, finding an ideal single-photon emitter (SPE) is a great challenge. Recently, two-dimensional (2D) materials have shown great potential as hosts for SPEs that are bright and operate under ambient conditions.[1]

These materials exhibit quantum properties that are generally absent in their bulk counterparts; which includes a layer-dependent bandgap, large exciton binding energies, strong nonlinearities, tunable valley degree of freedom, the ability to host quantum emitters and spin-defects. Moreover, due to their atomic thicknesses, 2D materials can be easily be integrated with electronic and photonic devices, facilitating precise engineering of light–matter interaction at the nanoscale.[2]

It is believed that the atomic defects and strains are responsible for creating single photon sites in such materials. However, deterministic control of such defects and strains have been always a challenge in this field.

**Project: **Therefore, the master project will include engineering as well as characterizing the single photon emitters mainly in 2D materials. Deterministic creation of the SPE centers at predefined locations will be the main aim for this project. The student will also perform the second order correlation measurements to investigate the purity of the emitters. A Hanbury-Brown and Twiss (HBT) interferometer will be used to perform the autocorrelation measurements. Others important factors such as indistinguishability, brightness, and reliability of the emitters will also be investigated.

Figure 1. (a) Material defects with well-defined spin-state and consequently polarized single-photon emission can be building blocks of spin–photonic qubit systems. (b) A schematic of a two-level system, which is paramagnetic and is well separated from the band edges and can emit single photons in the required Fourier transform (FT) limit, such that the broadening of emission in the spectral line Γ equals the inverse of the excited-state decay lifetime Γ = ℏ/τ. (c) A typical second-order photon correlation measurement plot g2(τ), as a function of delay time τ, depicting antibunching (no more than one photon is emitted at a time). A value of g2(τ = 0) < 0.5 is a signature of a “good” single-photon, as this quantity is connected to the probability of emitting two photons (or more) at the same time.

**References:**

[1] J. Phys. Chem. Lett. 14, 3274 (2023)

[2] Appl. Phys. Lett. 118, 240502 (2021)

#### Project listed by Dr. Junichiro Kono (kono@rice.edu)

**Title: Cavity Quantum Electrodynamics in Quantum Materials**

**Context: **There is currently much interest in studying solids placed in cavities to uncover exotic new phases and phenomena in “strongly driven” materials in the complete absence of any external fields other than the fluctuating vacuum, or zero-point, electromagnetic fields [1–3]. Judicious engineering of the quantum vacuum surrounding the matter inside the cavity can lead to significant and nonintuitive modifications of electronic states, producing a vacuum-dressed material with novel properties. Recent stimulating theoretical predictions include cavity-enhanced, cavity-induced, and cavity-mediated enhancement of electron-phonon coupling and superconductivity, electron pairing, anomalous Hall effect, ferroelectric phase transitions, quantum spin liquids, and photon condensation. The figure above highlights the opportunities in the cavity-matter interactions leading to several exotic phenomena ranging from the formation of polaritonics to nonlinear optics. Exciting experimental observations have been made in materials placed in cavities as well, including observations of the vacuum Bloch-Siegert shift [4,5], vacuum-field-induced resistivity modifications, large enhancement of ferromagnetism in YBCO nanoparticles, and an increase of the superconducting transition temperature in Rb3C60. These pioneering studies have demonstrated the feasibility of manipulating materials’ macroscopic properties by cavity vacuum fields.

**Project: **The REU fellow’s research will focus on the design, fabrication, and characterization of novel optical cavities, especially in the terahertz frequency range, with ultrahigh Q-factors and ultrasmall mode volumes. Low-dimensional materials such as carbon nanotubes, graphene, and transition metal dichalcogenides as well as thin films of superconductors, ferroelectrics, and strongly correlated materials will be studied inside the developed cavities using optical, electronic/thermal transport, and magnetic methods. Furthermore, if time permits, the REU fellow will use ultrafast optical techniques to demonstrate macroscopic two-mode quantum squeezing, expected to exist in the ground state of an ultrastrongly coupled system. He/she will specifically study spin-magnon ultrastrong coupling in rare-earth orthoferrites [6,7] to search for the optimum conditions for maximizing the coupling strength and the squeezing parameter. A novel apparatus will be developed for optomagnonic measurements of quantum fluctuations.

**References:**

- T. W. Ebbesen, “Hybrid Light–Matter States in a Molecular and Material Science Perspective,” Acc. Chem. Res. 49, 2403 (2016).
- F. J. Garcia-Vidal, C. Ciuti, and T. W. Ebbesen, “Manipulating Matter by Strong Coupling to Vacuum Fields,” Science 373, eabd0336 (2021).
- H. Hübener, U. De Giovannini, C. Sch¨afer, J. Andberger, M. Ruggenthaler, J. Faist, and A. Rubio, “Engineering Quantum Materials with Chiral Optical Cavities,” Nat. Mater. 20, 438 (2021).
- X. Li, M. Bamba, Q. Zhang, M. Lou, J. D. Watson, K. Yoshioka, M. J. Manfra, and J. Kono, “Vacuum Bloch-Siegert Shift in Landau Polaritons with Ultrahigh Cooperativity,” Nature Photonics 12, 324 (2018).
- T. Makihara, K. Hayashida, G. T. Noe II, X. Li, N. Marquez Peraca, X. Ma, Z. Jin, W. Ren, G. Ma, I. Katayama, J. Takeda, H. Nojiri, D. Turchinovich, S. Cao, M. Bamba, and J. Kono, “Ultrastrong Magnon-Magnon Coupling Dominated by Antiresonant Interactions,” Nature Communications 12, 3115 (2021).
- X. Li, M. Bamba, N. Yuan, Q. Zhang, Y. Zhao, M. Xiang, K. Xu, Z. Jin, W. Ren, G. Ma, S. Cao, D. Turchinovich, and J. Kono, “Observation of Dicke Cooperativity in Magnetic Interactions,” Science 361, 794 (2018).
- M. Bamba, X. Li, N. Marquez Peraca, and J. Kono, “Magnonic Superradiant Phase Transition,” Communications Physics 5, 3 (2022).

#### Project listed by Dr. Thomas C. Killian (killian@rice.edu)

**Title: Quantum simulation with ultracold Rydberg atoms**

**Project:** Rydberg atoms are atoms in which an electron has been excited to an extremely weakly bound orbit that takes it far from the nucleus. Ultracold Rydberg atoms are a promising platform for quantum simulation of many-body physics because they have strong, controllable interactions and internal quantum states that can be mapped to properties of more complex materials or other many-body systems that are beyond the capabilities of classical computer calculations to describe. Prof. Killian’s group at Rice has pioneered the study of quantum degenerate gases and Rydberg atoms of alkaline-earth atoms (http://ultracold.rice.edu/), and we are currently developing new techniques to create large networks of internal atomic states for more flexible quantum simulation to study topological states of matter and magnetic interactions. On this project, the REU fellow will learn to operate lasers and electronic equipment in order to produce and trap ultracold atoms and excite them to Rydberg states. The student will also analyze images of atomic clouds and data from charged-particle detection diagnostics in order to study the internal state dynamics of many-body, interacting systems of Rydberg atoms. This project will train the student in the techniques of laser-cooling and trapping of atoms, coherent manipulation of atomic states with lasers and millimeter-wave radiation, and general laboratory techniques in computer experimental control and data acquisition, electronics, vacuum, and optics at the frontier of atomic, molecular, and optical physics.