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Ph.D Electrical Engineering, Princeton University (2019) B.A Physics Middlebury College (2013)
Mattias hails from the great state of Oregon and is a graduate of Middlebury College. He became a member of the lab in 2013 and worked on nonequilibrium phase... Read more about Mattias Fitzpatrick
Zhaoqi Leng joined the lab in 2015. He worked on creating and stabilizing entanglement in circuit QED systems. He is researching new optimization/machine... Read more about Zhaoqi Leng
Master of Science in Physics from Indian Institute of Science (IISc) [2016] Bachelor of Science (Research) in Physics with Distinction from Indian Institute of Science (IISc) [2015]
Pranav hails from Nasik, the wine capital of India, but he does not know his wines. On finding a problem interesting and impactful enough, he does not hesitate... Read more about Pranav Mundada
Alex finished his PhD with the group in 2022. He built and studied qubits which are intrinsically insensitive to noise. Alex grew up in Arlington VA and... Read more about Alex Place
Srikanth Srinivasan was brave enough to be the first graduate student in the Houck Lab. While he was a graduate student, he worked on both the tunable coupling... Read more about Srikanth Srinivasan
Neereja became a member of the lab in the spring of 2013. She studied the ultra-low frequency regime in circuit QED and explored the interactions that arise... Read more about Neereja Sundaresan
Ph.D. Princeton University B.S Physics and Mathematics University of Wisconsin- River Falls
Devin Underwood works on arrays of cQED elements for purposes of studying condensed matter physics with photons. He hales from frosty Alaska, and is known for... Read more about Devin Underwood
Andrei joined the HouckLab in 2015 after finishing his undergraduate studies at University College London. His work has been focused on engineering photon... Read more about Andrei Vrajitoarea
Ph.D Electrical Engineering, Princeton University (2018) M.S Electrical Engineering, Tsinghua University (2011) B.S Electrical Engineering, Tsinghua University (2008)
Gengyan became a member of the Houck Lab in 2011 after receiving his bachelor's and master's degree from Tsinghua University. Known in the group as the fab... Read more about Gengyan Zhang
Near-term quantum computers are primarily limited by errors in quantum operations (or gates) between two quantum bits (or qubits). A physical machine typically provides a set of basis gates that include primitive 2-qubit (2Q) and 1-qubit (1Q) gates that can be implemented in a given technology. 2Q entangling gates, coupled with some 1Q gates, allow for universal quantum computation. In superconducting technologies, the current state of the art is to implement the same 2Q gate between every pair of qubits (typically an XX- or XY-type gate). This strict hardware uniformity requirement for 2Q gates in a large quantum computer has made scaling up a time and resource-intensive endeavor in the lab. We propose a radical idea -- allow the 2Q basis gate(s) to differ between every pair of qubits, selecting the best entangling gates that can be calibrated between given pairs of qubits. This work aims to give quantum scientists the ability to run meaningful algorithms with qubit systems that are not perfectly uniform. Scientists will also be able to use a much broader variety of novel 2Q gates for quantum computing. We develop a theoretical framework for identifying good 2Q basis gates on "nonstandard" Cartan trajectories that deviate from "standard" trajectories like XX. We then introduce practical methods for calibration and compilation with nonstandard 2Q gates, and discuss possible ways to improve the compilation. To demonstrate our methods in a case study, we simulated both standard XY-type trajectories and faster, nonstandard trajectories using an entangling gate architecture with far-detuned transmon qubits. We identify efficient 2Q basis gates on these nonstandard trajectories and use them to compile a number of standard benchmark circuits such as QFT and QAOA. Our results demonstrate an 8x improvement over the baseline 2Q gates with respect to speed and coherence-limited gate fidelity.
Recent theoretical work has highlighted that quantizing a superconducting circuit in the presence of time- dependent flux Φ(t) generally produces Hamiltonian terms proportional to dΦ/dt unless a special allocation of the flux across inductive terms is chosen. Here, we present an experiment probing the effects of a fast flux ramp applied to a heavy-fluxonium circuit. The experiment confirms that na ̈ıve omission of the dΦ/dt term leads to theoretical predictions inconsistent with experimental data. Experimental data are fully consistent with recent theory that includes the derivative term or equivalently uses “irrotational variables” that uniquely allocate the flux to properly eliminate the dΦ/dt term.
We introduce a Xilinx RF System-on-Chip (RFSoC)-based qubit controller (called the Quantum Instrumentation Control Kit, or QICK for short), which supports the direct synthesis of control pulses with carrier frequencies of up to 6 GHz. The QICK can control multiple qubits or other quantum devices. The QICK consists of a digital board hosting an RFSoC field-programmable gate array, custom firmware, and software and an optional companion custom-designed analog front-end board. We characterize the analog performance of the system as well as its digital latency, important for quantum error correction and feedback protocols. We benchmark the controller by performing standard characterizations of a transmon qubit. We achieve an average gate fidelity of F=99.93%. All of the schematics, firmware, and software are open-source.
The origin of many quantum-material phenomena is intimately related to the presence of flat electronic bands. In quantum simulation, such bands have been realized through line-graph lattices, a class of lattices known to exhibit flat bands. Based on that work, we conduct a high-throughput screening for line-graph lattices among the crystalline structures of the Materials Flatband Database and report on new candidates for line-graph materials and lattice models. In particular, we find materials with line-graph-lattice structures beyond the two most commonly known examples, the kagomé and pyrochlore lattices. We also identify materials which may exhibit flat topological bands. Finally, we examine the various line-graph lattices detected and highlight those with gapped flat bands and those most frequently represented among this set of materials. With the identification of real stoichiometric materials and theoretical lattice geometries, the results of this work may inform future studies of flat-band many-body physics in both condensed matter experiment and theory.
