M. Neeley

Google (United States)

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Co-Authors

Erik Lucero

Google (United States)

130

D. Sank

Google (United States)

111

John M. Martinis

Tektronix (United States)

110

J. Kelly

Google (United States)

A. Megrant

Google (United States)

P. Roushan

Google (United States)

T. White

Google (United States)

Chris Quintana

Google (United States)

E. Jeffrey

Google (United States)

A. Dunsworth

Google (United States)

Cooperative Institutions

Google (United States)

487

University of California, Riverside

173

University of California, Santa Barbara

University of California, Berkeley

Harvard University

California Institute of Technology

Lawrence Berkeley National Laboratory

Massachusetts Institute of Technology

Ames Research Center

National Institute of Standards and Technology

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Research Field

Measuring and Suppressing Quantum State Leakage in a Superconducting Qubit

Physical Review Letters (2016)

Zijun Chen J. Kelly Chris Quintana R. Barends B. Campbell

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 leakage errors, we use randomized benchmarking in conjunction with measurement of the leakage population. We characterize single qubit gates in a superconducting qubit, and by refining our use of derivative reduction by adiabatic gate pulse shaping along with detuning of the pulses, we obtain gate errors consistently below 10^{-3} and leakage rates at the 10^{-5} level. With the control optimized, we find that a significant portion of the remaining leakage is due to incoherent heating of the qubit.

Leakage (economics)

10.1103/physrevlett.116.020501

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Citations (213)

A method for building low loss multi-layer wiring for superconducting microwave devices

Applied Physics Letters (2018)

A. Dunsworth R. Barends Yu Chen Zijun Chen B. Chiaro

Complex integrated circuits require multiple wiring layers. In complementary metal-oxide-semiconductor processing, these layers are robustly separated by amorphous dielectrics. These dielectrics would dominate energy loss in superconducting integrated circuits. Here, we describe a procedure that capitalizes on the structural benefits of inter-layer dielectrics during fabrication and mitigates the added loss. We use a deposited inter-layer dielectric throughout fabrication and then etch it away post-fabrication. This technique is compatible with foundry level processing and can be generalized to make many different forms of low-loss wiring. We use this technique to create freestanding aluminum vacuum gap crossovers (airbridges). We characterize the added capacitive loss of these airbridges by connecting ground planes over microwave frequency λ/4 coplanar waveguide resonators and measuring resonator loss. We measure a low power resonator loss of ∼3.9 × 10−8 per bridge, which is 100 times lower than that of dielectric supported bridges. We further characterize these airbridges as crossovers, control line jumpers, and as part of a coupling network in gmon and fluxmon qubits. We measure qubit characteristic lifetimes (T1s) in excess of 30 μs in gmon devices.

Dielectric loss

Coplanar waveguide

10.1063/1.5014033

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Citations (45)

Microwave response of vortices in superconducting thin films of Re and Al

Physical Review B (2009)

Chao Song Tom Heitmann M. P. DeFeo K. Yu R. McDermott

Vortices in superconductors driven at microwave frequencies exhibit a response related to the interplay between the vortex viscosity, pinning strength, and flux creep effects. At the same time, the trapping of vortices in superconducting microwave resonant circuits contributes excess loss and can result in substantial reductions in the quality factor. Thus, understanding the microwave vortex response in superconducting thin films is important for the design of such circuits, including superconducting qubits and photon detectors, which are typically operated in small, but non-zero, magnetic fields. By cooling in fields of the order of 100 $μ$T and below, we have characterized the magnetic field and frequency dependence of the microwave response of a small density of vortices in resonators fabricated from thin films of Re and Al, which are common materials used in superconducting microwave circuits. Above a certain threshold cooling field, which is different for the Re and Al films, vortices become trapped in the resonators. Vortices in the Al resonators contribute greater loss and are influenced more strongly by flux creep effects than in the Re resonators. This different behavior can be described in the framework of a general vortex dynamics model.

10.1103/physrevb.79.174512

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Citations (141)

Generation of Three-Qubit Entanglement Using Josephson Phase Qubits

M. Neeley

Flux qubit

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Citations (7)

Emulation of a Quantum Spin with a Superconducting Phase Qudit

Science (2009)

M. Neeley M. Ansmann Radoslaw C. Bialczak M. Hofheinz Erik Lucero

In quantum information processing, qudits (d-level systems) are an extension of qubits that could speed up certain computing tasks. We demonstrate the operation of a superconducting phase qudit with a number of levels d up to d = 5 and show how to manipulate and measure the qudit state, including simultaneous control of multiple transitions. We used the qudit to emulate the dynamics of single spins with principal quantum number s = 1/2, 1, and 3/2, allowing a measurement of Berry's phase and the even parity of integer spins (and odd parity of half-integer spins) under 2pi-rotation. This extension of the two-level qubit to a multilevel qudit holds promise for more-complex quantum computational architectures and for richer simulations of quantum mechanical systems.

Parity (physics)

10.1126/science.1173440

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Citations (288)

Tuning Quantum Information Scrambling on a 53-Qubit Processor

Adam Zalcman Alan R. Derk Alan Ho Alex Opremcak Alexander N. Korotkov

Scrambling

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Reduced phase error through optimized control of a superconducting qubit

Physical Review A (2010)

Erik Lucero J. Kelly Radoslaw C. Bialczak M. Lenander M. Mariantoni

Minimizing phase and other errors in experimental quantum gates allows higher fidelity quantum processing. To quantify and correct for phase errors, in particular, we have developed an experimental metrology---amplified phase error (APE) pulses---that amplifies and helps identify phase errors in general multilevel qubit architectures. In order to correct for both phase and amplitude errors specific to virtual transitions and leakage outside of the qubit manifold, we implement ``half derivative,'' an experimental simplification of derivative reduction by adiabatic gate (DRAG) control theory. The phase errors are lowered by about a factor of five using this method to $~{1.6}^{\ifmmode^\circ\else\textdegree\fi{}}$ per gate, and can be tuned to zero. Leakage outside the qubit manifold, to the qubit $|2\ensuremath{\rangle}$ state, is also reduced to $~{10}^{\ensuremath{-}4}$ for $20%$ faster gates.

Leakage (economics)

10.1103/physreva.82.042339

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Citations (122)

Dynamic quantum Kerr effect in circuit quantum electrodynamics

Physical Review Letters (2011)

Yi Yin H. Wang M. Mariantoni Radoslaw C. Bialczak R. Barends

A superconducting qubit coupled to a microwave resonator provides a controllable system that enables fundamental studies of light-matter interactions. In the dispersive regime, photons in the resonator exhibit induced frequency and phase shifts which are revealed in the resonator transmission spectrum measured with fixed qubit-resonator detuning. In this static detuning scheme, the phase shift is measured in the far-detuned, linear dispersion regime to avoid measurement-induced demolition of the qubit quantum state. Here we explore the qubit-resonator dispersive interaction over a much broader range of detunings, by using a dynamic procedure where the qubit transition is driven adiabatically. We use resonator Wigner tomography to monitor the interaction, revealing exotic non-linear effects on different photon states, e.g., Fock states, coherent states, and Schrodinger cat states, thereby demonstrating a quantum Kerr effect in the dynamic framework.

Circuit quantum electrodynamics

Charge qubit

Flux qubit

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Citations (68)

Noise-resilient Edge Modes on a Chain of Superconducting Qubits

arXiv (Cornell University) (2022)

Mi Xiao Michael Sonner Murphy Yuezhen Niu Kenneth W. Lee Brooks Foxen

Inherent symmetry of a quantum system may protect its otherwise fragile states. Leveraging such protection requires testing its robustness against uncontrolled environmental interactions. Using 47 superconducting qubits, we implement the one-dimensional kicked Ising model which exhibits non-local Majorana edge modes (MEMs) with $\mathbb{Z}_2$ parity symmetry. Remarkably, we find that any multi-qubit Pauli operator overlapping with the MEMs exhibits a uniform late-time decay rate comparable to single-qubit relaxation rates, irrespective of its size or composition. This characteristic allows us to accurately reconstruct the exponentially localized spatial profiles of the MEMs. Furthermore, the MEMs are found to be resilient against certain symmetry-breaking noise owing to a prethermalization mechanism. Our work elucidates the complex interplay between noise and symmetry-protected edge modes in a solid-state environment.

Chain (unit)

10.48550/arxiv.2204.11372

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Citations (3)

Experimental bring-up procedures with metrology to improve superconducting qubit performance

Bulletin of the American Physical Society (2010)

Erik Lucero J. Kelly Radoslaw C. Bialczak M. Lenander M. Mariantoni

Quantum Metrology

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