# Irfan Siddiqi

Irfan Siddiqi is a faculty scientist in the QuIST group in Berkeley Lab's Computational Research Division. In addition to directing QuIST's Advanced Quantum Testbed (AQT), Siddiqi is a professor of physics at the University of California Berkeley and director of the Quantum Nanoelectronics Laboratory at UC Berkeley.

Siddiqi is known for his groundbreaking contributions to the fields of superconducting quantum circuits, including dispersive single-shot readout of superconducting quantum bits, quantum feedback, observation of single quantum trajectories, and near-quantum limited microwave frequency amplification.

He is a fellow of the American Physical Society and a recipient of the American Physical Society George E. Valley, Jr. Prize "for the development of the Josephson bifurcation amplifier for ultra-sensitive measurements at the quantum limit."

Siddqi earned his Ph.D. in applied physics from Yale University in 2002. He received his undergraduate degree from Harvard University in 1997.

## Journal Articles

### JM Kreikebaum, KP O Brien, A Morvan, I Siddiqi, "Improving wafer-scale Josephson junction resistance variation in superconducting quantum coherent circuits", Superconductor Science and Technology, 2020, 33, doi: 10.1088/1361-6668/ab8617

### LS Martin, WP Livingston, S Hacohen-Gourgy, HM Wiseman, I Siddiqi, "Implementation of a canonical phase measurement with quantum feedback", Nature Physics, 2020, 16:1046--1049, doi: 10.1038/s41567-020-0939-0

### E Flurin, LS Martin, S Hacohen-Gourgy, I Siddiqi, "Using a Recurrent Neural Network to Reconstruct Quantum Dynamics of a Superconducting Qubit from Physical Observations", Physical Review X, 2020, 10, doi: 10.1103/PhysRevX.10.011006

### S Schaal, I Ahmed, JA Haigh, L Hutin, B Bertrand, S Barraud, M Vinet, C-M Lee, N Stelmashenko, JWA Robinson, JY Qiu, S Hacohen-Gourgy, I Siddiqi, MF Gonzalez-Zalba, JJL Morton, "Fast Gate-Based Readout of Silicon Quantum Dots Using Josephson Parametric Amplification.", Physical review letters, 2020, 124:067701, doi: 10.1103/physrevlett.124.067701

### J Atalaya, S Hacohen-Gourgy, I Siddiqi, AN Korotkov, "Correlators Exceeding One in Continuous Measurements of Superconducting Qubits.", Physical review letters, 2019, 122:223603, doi: 10.1103/physrevlett.122.223603

### A Eddins, JM Kreikebaum, DM Toyli, EM Levenson-Falk, A Dove, WP Livingston, BA Levitan, LCG Govia, AA Clerk, I Siddiqi, "High-Efficiency Measurement of an Artificial Atom Embedded in a Parametric Amplifier", Physical Review X, 2019, 9, doi: 10.1103/PhysRevX.9.011004

### JI Colless, VV Ramasesh, D Dahlen, MS Blok, ME Kimchi-Schwartz, JR McClean, J Carter, WA De Jong, I Siddiqi, "Computation of Molecular Spectra on a Quantum Processor with an Error-Resilient Algorithm", Physical Review X, 2018, 8, doi: 10.1103/PhysRevX.8.011021

### J Atalaya, S Hacohen-Gourgy, LS Martin, I Siddiqi, AN Korotkov, "Correlators in simultaneous measurement of non-commuting qubit observables", npj Quantum Information, 2018, 4, doi: 10.1038/s41534-018-0091-1

### J Atalaya, S Hacohen-Gourgy, LS Martin, I Siddiqi, AN Korotkov, "Multitime correlators in continuous measurement of qubit observables", Physical Review A, 2018, 97, doi: 10.1103/PhysRevA.97.020104

### S Hacohen-Gourgy, LP García-Pintos, LS Martin, J Dressel, I Siddiqi, "Incoherent Qubit Control Using the Quantum Zeno Effect.", Physical review letters, 2018, 120:020505, doi: 10.1103/physrevlett.120.020505

### A Chantasri, J Atalaya, S Hacohen-Gourgy, LS Martin, I Siddiqi, AN Jordan, "Simultaneous continuous measurement of noncommuting observables: Quantum state correlations", Physical Review A, 2018, 97, doi: 10.1103/PhysRevA.97.012118

### A Eddins, S Schreppler, DM Toyli, LS Martin, S Hacohen-Gourgy, LCG Govia, H Ribeiro, AA Clerk, I Siddiqi, "Stroboscopic Qubit Measurement with Squeezed Illumination.", Physical review letters, 2018, 120:040505, doi: 10.1103/physrevlett.120.040505

### KA Fischer, R Trivedi, V Ramasesh, I Siddiqi, J Vuckovic, "Scattering into one-dimensional waveguides from a coherently-driven quantum-optical system", Quantum, 2018, 2, doi: 10.22331/q-2018-05-28-69

### VV Ramasesh, E Flurin, M Rudner, I Siddiqi, NY Yao, "Direct Probe of Topological Invariants Using Bloch Oscillating Quantum Walks.", Physical review letters, 2017, 118:130501, doi: 10.1103/physrevlett.118.130501

### E Flurin, VV Ramasesh, S Hacohen-Gourgy, LS Martin, NY Yao, I Siddiqi, "Observing topological invariants using quantum walks in superconducting circuits", Physical Review X, 2017, 7, doi: 10.1103/PhysRevX.7.031023

### S Boutin, DM Toyli, AV Venkatramani, AW Eddins, I Siddiqi, A Blais, "Effect of Higher-Order Nonlinearities on Amplification and Squeezing in Josephson Parametric Amplifiers", Physical Review Applied, 2017, 8, doi: 10.1103/PhysRevApplied.8.054030

### SJ Weber, KW Murch, ME Kimchi-Schwartz, N Roch, I Siddiqi, "Quantum trajectories of superconducting qubits", Comptes Rendus Physique, 2016, 17:766--777, doi: 10.1016/j.crhy.2016.07.007

### DH Slichter, C Müller, R Vijay, SJ Weber, A Blais, I Siddiqi, "Quantum Zeno effect in the strong measurement regime of circuit quantum electrodynamics", New Journal of Physics, 2016, 18, doi: 10.1088/1367-2630/18/5/053031

### ME Kimchi-Schwartz, L Martin, E Flurin, C Aron, M Kulkarni, HE Tureci, I Siddiqi, "Stabilizing Entanglement via Symmetry-Selective Bath Engineering in Superconducting Qubits.", Physical review letters, 2016, 116:240503, doi: 10.1103/physrevlett.116.240503

### S Hacohen-Gourgy, LS Martin, E Flurin, VV Ramasesh, KB Whaley, I Siddiqi, "Quantum dynamics of simultaneously measured non-commuting observables.", Nature, 2016, 538:491--494, doi: 10.1038/nature19762

### A Chantasri, ME Kimchi-Schwartz, N Roch, I Siddiqi, AN Jordan, "Quantum trajectories and their statistics for remotely entangled quantum bits", Physical Review X, 2016, 6, doi: 10.1103/PhysRevX.6.041052

### C Macklin, K O Brien, D Hover, ME Schwartz, V Bolkhovsky, X Zhang, WD Oliver, I Siddiqi, "A near-quantum-limited Josephson traveling-wave parametric amplifier.", Science (New York, N.Y.), 2015, 350:307--310, doi: 10.1126/science.aaa8525

### SJ Weber, A Chantasri, J Dressel, AN Jordan, KW Murch, I Siddiqi, "Mapping the optimal route between two quantum states.", Nature, 2014, 511:570--573, doi: 10.1038/nature13559

### KW Murch, SJ Weber, C Macklin, I Siddiqi, "Observing single quantum trajectories of a superconducting quantum bit", Nature, 2013, 502:211--214, doi: 10.1038/nature12539

## Conference Papers

### Anastasiia Butko, George Michelogiannakis, Samuel Williams, Costin Iancu, David Donofrio, John Shalf, Jonathan Carter, Irfan Siddiqi, "Understanding Quantum Control Processor Capabilities and Limitations through Circuit Characterization", IEEE Conference on Rebooting Computing (ICRC), December 2020,

- Download File: ICRC20-QUASAR-final.pdf (pdf: 1.1 MB)

### Marc G. Davis, Ethan Smith, Ana Tudor, Koushik Sen, Irfan Siddiqi, Costin Iancu, "Towards Optimal Topology Aware Quantum Circuit Synthesis", 2020 IEEE International Conference on Quantum Computing and Engineering (QCE), Denver, CO, USA, IEEE, October 12, 2020, doi: 10.1109/QCE49297.2020.00036

We present an algorithm for compiling arbitrary unitaries into a sequence of gates native to a quantum processor. As CNOT gates are error-prone for the foreseeable Noisy-Intermediate-Scale Quantum devices era, our A* inspired algorithm minimizes their count while accounting for connectivity. We discuss the formulation of synthesis as a search problem as well as an algorithm to find solutions. For a workload of circuits with complexity appropriate for the NISQ era, we produce solutions well within the best upper bounds published in literature and match or exceed hand tuned implementations, as well as other existing synthesis alternatives. In particular, when comparing against state-of-the-art available synthesis packages we show 2.4× average (up to 5.3×) reduction in CNOT count. We also show how to re-target the algorithm for a different chip topology and native gate set while obtaining similar quality results. We believe that tools like ours can facilitate algorithmic exploration and guide gate set discovery for quantum processor designers, as well as being useful for optimization in the quantum compilation tool-chain.

### Marc Grau Davis, Ethan Smith, Ana Tudor, Koushik Sen, Irfan Siddiqi, Costin Iancu, "Heuristics for Quantum Compiling with a Continuous Gate Set", 3rd International Workshop on Quantum Compilation as part of the International Conference On Computer Aided Design 2019, December 5, 2019,

We present an algorithm for compiling arbitrary unitaries into a sequence of gates native to a quantum processor. As accurate CNOT gates are hard for the foreseeable Noisy- Intermediate-Scale Quantum devices era, our A* inspired algorithm attempts to minimize their count, while accounting for connectivity. We discuss the search strategy together with metrics to expand the solution frontier. For a workload of circuits with complexity appropriate for the NISQ era, we produce solutions well within the best upper bounds published in literature and match or exceed hand tuned implementations, as well as other existing synthesis alternatives. In particular, when comparing against state-of-the-art available synthesis packages we show 2.4x average (up to 5.3x) reduction in CNOT count. We also show how to re-target the algorithm for a different chip topology and native gate set, while obtaining similar quality results. We believe that empirical tools like ours can facilitate algorithmic exploration, gate set discovery for quantum processor designers, as well as providing useful optimization blocks within the quantum compilation tool-chain.

## Others

### Akel Hashim, Ravi Naik, Alexis Morvan, Jean-Loup Ville, Brad Mitchell, John Mark Kreikebaum, Marc Davis, Ethan Smith, Costin Iancu, Kevin O Brien, Ian Hincks, Joel Wallman, Joseph V Emerson, David Ivan Santiago, Irfan Siddiqi, Scalable Quantum Computing on a Noisy Superconducting Quantum Processor via Randomized Compiling, Bulletin of the American Physical Society, 2021,

Coherent errors in quantum hardware severely limit the performance of quantum algorithms in an unpredictable manner, and mitigating their impact is necessary for realizing reliable, large-scale quantum computations. Randomized compiling achieves this goal by converting coherent errors into stochastic noise, dramatically reducing unpredictable errors in quantum algorithms and enabling accurate predictions of aggregate performance via cycle benchmarking estimates. In this work, we demonstrate significant performance gains under randomized compiling for both the four-qubit quantum Fourier transform algorithm and for random circuits of variable depth on a superconducting quantum processor. We also validate solution accuracy using experimentally-measured error rates. Our results demonstrate that randomized compiling can be utilized to maximally-leverage and predict the capabilities of modern-day noisy quantum processors, paving the way forward for scalable quantum computing.