Publications (49)
Scalable Quantum Simulation of Molecular Energies
P. J. J. O'Malley, R. Babbush, I. D. Kivlichan +27
We report the first electronic structure calculation performed on a quantum computer without exponentially costly precompilation. We use a programmable array of superconducting qub…
Characterization and Reduction of Capacitive Loss Induced by Sub-Micron Josephson Junction Fabrication in Superconducting Qubits
A. Dunsworth, A. Megrant, C. Quintana +20
Josephson junctions form the essential non-linearity for almost all superconducting qubits. The junction is formed when two superconducting electrodes come within 1 nm of eac…
Quantum computation of molecular geometry via many-body nuclear spin echoes
C. Zhang, R. G. Cortiñas, A. H. Karamlou +320
Quantum-information-inspired experiments in nuclear magnetic resonance spectroscopy may yield a pathway towards determining molecular structure and properties that are otherwise ch…
Ergodic dynamics and thermalization in an isolated quantum system
C. Neill, P. Roushan, M. Fang +19
Statistical mechanics is founded on the assumption that all accessible configurations of a system are equally likely. This requires dynamics that explore all states over time, know…
Measurement-induced state transitions in a superconducting qubit: Beyond the rotating wave approximation
Daniel Sank, Zijun Chen, Mostafa Khezri +21
Many superconducting qubit systems use the dispersive interaction between the qubit and a coupled harmonic resonator to perform quantum state measurement. Previous works have found…
Stable Quantum-Correlated Many Body States through Engineered Dissipation
X. Mi, A. A. Michailidis, S. Shabani +164
Engineered dissipative reservoirs have the potential to steer many-body quantum systems toward correlated steady states useful for quantum simulation of high-temperature supercondu…
Phase transition in Random Circuit Sampling
A. Morvan, B. Villalonga, X. Mi +182
Undesired coupling to the surrounding environment destroys long-range correlations on quantum processors and hinders the coherent evolution in the nominally available computational…
Simulating weak localization using superconducting quantum circuits
Yu Chen, P. Roushan, D. Sank +15
Understanding complex quantum matter presents a central challenge in condensed matter physics. The difficulty lies in the exponential scaling of the Hilbert space with the system s…
Catching Shaped Microwave Photons with 99.4% Absorption Efficiency
J. Wenner, Yi Yin, Yu Chen +15
We demonstrate a high efficiency deterministic quantum receiver to convert flying qubits to logic qubits. We employ a superconducting resonator, which is driven with a shaped pulse…
Direct measurement of non-local interactions in the many-body localized phase
B. Chiaro, C. Neill, A. Bohrdt +58
The interplay of interactions and strong disorder can lead to an exotic quantum many-body localized (MBL) phase. Beyond the absence of transport, the MBL phase has distinctive sign…
Digital quantum simulation of fermionic models with a superconducting circuit
R. Barends, L. Lamata, J. Kelly +21
Simulating quantum physics with a device which itself is quantum mechanical, a notion Richard Feynman originated, would be an unparallelled computational resource. However, the uni…
Observation of classical-quantum crossover of 1/f flux noise and its paramagnetic temperature dependence
C. M. Quintana, Yu Chen, D. Sank +25
By analyzing the dissipative dynamics of a tunable gap flux qubit, we extract both sides of its two-sided environmental flux noise spectral density over a range of frequencies arou…
Controlled catch and release of microwave photon states
Yi Yin, Yu Chen, Daniel Sank +13
The quantum behavior of superconducting qubits coupled to resonators is very similar to that of atoms in optical cavities [1, 2], in which the resonant cavity confines photons and…
Qubit compatible superconducting interconnects
B. Foxen, J. Y. Mutus, E. Lucero +27
We present a fabrication process for fully superconducting interconnects compatible with superconducting qubit technology. These interconnects allow for the 3D integration of quant…
Logic gates at the surface code threshold: Superconducting qubits poised for fault-tolerant quantum computing
R. Barends, J. Kelly, A. Megrant +19
A quantum computer can solve hard problems - such as prime factoring, database searching, and quantum simulation - at the cost of needing to protect fragile quantum states from err…
Coherent Josephson qubit suitable for scalable quantum integrated circuits
R. Barends, J. Kelly, A. Megrant +13
We demonstrate a planar, tunable superconducting qubit with energy relaxation times up to 44 microseconds. This is achieved by using a geometry designed to both minimize radiative…
Realizing topologically ordered states on a quantum processor
K. J. Satzinger, Y. Liu, A. Smith +95
The discovery of topological order has revolutionized the understanding of quantum matter in modern physics and provided the theoretical foundation for many quantum error correctin…
High speed flux sampling for tunable superconducting qubits with an embedded cryogenic transducer
B. Foxen, J. Y. Mutus, E. Lucero +26
We develop a high speed on-chip flux measurement using a capacitively shunted SQUID as an embedded cryogenic transducer and apply this technique to the qualification of a near-term…
Scalable in-situ qubit calibration during repetitive error detection
J. Kelly, R. Barends, A. G. Fowler +19
We present a method to optimize qubit control parameters during error detection which is compatible with large-scale qubit arrays. We demonstrate our method to optimize single or t…
Multiplexed dispersive readout of superconducting phase qubits
Yu Chen, D. Sank, P. O'Malley +13
We introduce a frequency-multiplexed readout scheme for superconducting phase qubits. Using a quantum circuit with four phase qubits, we couple each qubit to a separate lumped-elem…
Characterization and reduction of microfabrication-induced decoherence in superconducting quantum circuits
C. M. Quintana, A. Megrant, Z. Chen +18
Many superconducting qubits are highly sensitive to dielectric loss, making the fabrication of coherent quantum circuits challenging. To elucidate this issue, we characterize the i…
A blueprint for demonstrating quantum supremacy with superconducting qubits
C. Neill, P. Roushan, K. Kechedzhi +25
Fundamental questions in chemistry and physics may never be answered due to the exponential complexity of the underlying quantum phenomena. A desire to overcome this challenge has…
Demonstrating a Continuous Set of Two-qubit Gates for Near-term Quantum Algorithms
B. Foxen, C. Neill, A. Dunsworth +54
Quantum algorithms offer a dramatic speedup for computational problems in machine learning, material science, and chemistry. However, any near-term realizations of these algorithms…
Fluctuations From Edge Defects in Superconducting Resonators
C. Neill, A. Megrant, R. Barends +11
Superconducting resonators, used in astronomy and quantum computation, couple strongly to microscopic two-level defects. We monitor the microwave response of superconducting resona…
Surface loss simulations of superconducting coplanar waveguide resonators
J. Wenner, R. Barends, R. C. Bialczak +14
Losses in superconducting planar resonators are presently assumed to predominantly arise from surface-oxide dissipation, due to experimental losses varying with choice of materials…
High-Fidelity Measurement of a Superconducting Qubit using an On-Chip Microwave Photon Counter
A. Opremcak, C. H. Liu, C. Wilen +10
We describe an approach to the high-fidelity measurement of a superconducting qubit using an on-chip microwave photon counter. The protocol relies on the transient response of a di…
Fluctuations of Energy-Relaxation Times in Superconducting Qubits
P. V. Klimov, J. Kelly, Z. Chen +30
Superconducting qubits are an attractive platform for quantum computing since they have demonstrated high-fidelity quantum gates and extensibility to modest system sizes. Nonethele…
Spectral signatures of many-body localization with interacting photons
P. Roushan, C. Neill, J. Tangpanitanon +23
Statistical mechanics is founded on the assumption that a system can reach thermal equilibrium, regardless of the starting state. Interactions between particles facilitate thermali…
UCSB final report for the CSQ program: Review of decoherence and materials physics for superconducting qubits
John M. Martinis, A. Megrant
We review progress at UCSB on understanding the physics of decoherence in superconducting qubits. Although many decoherence mechanisms were studied and fixed in the last 5 years, t…
State preservation by repetitive error detection in a superconducting quantum circuit
J. Kelly, R. Barends, A. G. Fowler +19
Quantum computing becomes viable when a quantum state can be preserved from environmentally-induced error. If quantum bits (qubits) are sufficiently reliable, errors are sparse and…
Optimal quantum control using randomized benchmarking
J. Kelly, R. Barends, B. Campbell +19
We present a method for optimizing quantum control in experimental systems, using a subset of randomized benchmarking measurements to rapidly infer error. This is demonstrated to i…
Fast Scalable State Measurement with Superconducting Qubits
Daniel Sank, Evan Jeffrey, J. Y. Mutus +15
Progress in superconducting qubit experiments with greater numbers of qubits or advanced techniques such as feedback requires faster and more accurate state measurement. We have de…
Removing leakage-induced correlated errors in superconducting quantum error correction
M. McEwen, D. Kafri, Z. Chen +48
Quantum computing can become scalable through error correction, but logical error rates only decrease with system size when physical errors are sufficiently uncorrelated. During co…
Dielectric surface loss in superconducting resonators with flux-trapping holes
B. Chiaro, A. Megrant, A. Dunsworth +18
Surface distributions of two level system (TLS) defects and magnetic vortices are limiting dissipation sources in superconducting quantum circuits. Arrays of flux-trapping holes ar…
Excitation of superconducting qubits from hot non-equilibrium quasiparticles
J. Wenner, Yi Yin, Erik Lucero +15
Superconducting qubits probe environmental defects such as non-equilibrium quasiparticles, an important source of decoherence. We show that "hot" non-equilibrium quasiparticles, wi…
Low Loss Multi-Layer Wiring for Superconducting Microwave Devices
A. Dunsworth, A. Megrant, R. Barends +20
Complex integrated circuits require multiple wiring layers. In complementary metal-oxide-semiconductor (CMOS) processing, these layers are robustly separated by amorphous dielectri…
Traveling wave parametric amplifier with Josephson junctions using minimal resonator phase matching
T. C. White, J. Y. Mutus, I. -C. Hoi +18
Josephson parametric amplifiers have become a critical tool in superconducting device physics due to their high gain and quantum-limited noise. Traveling wave parametric amplifiers…
Digitized adiabatic quantum computing with a superconducting circuit
R. Barends, A. Shabani, L. Lamata +26
A major challenge in quantum computing is to solve general problems with limited physical hardware. Here, we implement digitized adiabatic quantum computing, combining the generali…
Accurately computing electronic properties of a quantum ring
C. Neill, T. McCourt, X. Mi +89
A promising approach to study condensed-matter systems is to simulate them on an engineered quantum platform. However, achieving the accuracy needed to outperform classical methods…
Planar Superconducting Resonators with Internal Quality Factors above One Million
A. Megrant, C. Neill, R. Barends +16
We describe the fabrication and measurement of microwave coplanar waveguide resonators with internal quality factors above 10 million at high microwave powers and over 1 million at…
Preserving entanglement during weak measurement demonstrated with a violation of the Bell-Leggett-Garg inequality
T. C. White, J. Y. Mutus, J. Dressel +18
Weak measurement has provided new insight into the nature of quantum measurement, by demonstrating the ability to extract average state information without fully projecting the sys…
Purification-based quantum error mitigation of pair-correlated electron simulations
T. E. O'Brien, G. Anselmetti, F. Gkritsis +173
An important measure of the development of quantum computing platforms has been the simulation of increasingly complex physical systems. Prior to fault-tolerant quantum computing,…
Chiral groundstate currents of interacting photons in a synthetic magnetic field
P. Roushan, C. Neill, A. Megrant +22
The intriguing many-body phases of quantum matter arise from the interplay of particle interactions, spatial symmetries, and external fields. Generating these phases in an engineer…
Observation of topological transitions in interacting quantum circuits
P. Roushan, C. Neill, Yu Chen +21
The discovery of topological phases in condensed matter systems has changed the modern conception of phases of matter. The global nature of topological ordering makes these phases…
Diabatic gates for frequency-tunable superconducting qubits
R. Barends, C. M. Quintana, A. G. Petukhov +43
We demonstrate diabatic two-qubit gates with Pauli error rates down to in as fast as 18 ns using frequency-tunable superconducting qubits. This is achieved by…
Qubit metrology of ultralow phase noise using randomized benchmarking
P. J. J. O'Malley, J. Kelly, R. Barends +20
A precise measurement of dephasing over a range of timescales is critical for improving quantum gates beyond the error correction threshold. We present a metrological tool, based o…
Measuring and Suppressing Quantum State Leakage in a Superconducting Qubit
Zijun Chen, Julian Kelly, Chris Quintana +20
Leakage errors occur when a quantum system leaves the two-level qubit subspace. Reducing these errors is critically important for quantum error correction to be viable. To quantify…
Qubit architecture with high coherence and fast tunable coupling
Yu Chen, C. Neill, P. Roushan +20
We introduce a superconducting qubit architecture that combines high-coherence qubits and tunable qubit-qubit coupling. With the ability to set the coupling to zero, we demonstrate…
Rolling quantum dice with a superconducting qubit
R. Barends, J. Kelly, A. Veitia +20
One of the key challenges in quantum information is coherently manipulating the quantum state. However, it is an outstanding question whether control can be realized with low error…