Bulletin of the American Physical Society
APS March Meeting 2019
Volume 64, Number 2
Monday–Friday, March 4–8, 2019; Boston, Massachusetts
Session H62: Novel Superconducting Qubits: Intrinsic Protection and Bath EngineeringFocus Invited
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Sponsoring Units: DQI Chair: Blake Johnson, Rigetti Quantum Computing Room: BCEC 258C |
Tuesday, March 5, 2019 2:30PM - 3:06PM |
H62.00001: Beyond the transmon: A new generation of superconducting qubits Invited Speaker: David Schuster TBD |
Tuesday, March 5, 2019 3:06PM - 3:42PM |
H62.00002: Entanglement and complexity of interacting transmon qubits subject to asymmetric noise Invited Speaker: Eliot Kapit The simulation complexity of predicting the time evolution of delocalized many-body quantum systems has attracted much recent interest, and simulations of such systems in real quantum hardware are promising routes to demonstrating a quantum advantage over classical machines. In these proposals, random noise is an obstacle that must be overcome for a faithful simulation, and a single error event can be enough to drive the system to a classically trivial state. We argue that this need not always be the case, and consider a modification to a leading quantum sampling problem-- time evolution in an interacting Bose-Hubbard chain of transmon qubits [Neill et al, Science 360, 195 (2018)] -- where each site in the chain has a driven coupling to a lossy resonator and particle number is no longer conserved. The resulting quantum dynamics are complex and highly nontrivial. We show that this problem is likely to be harder to simulate than the isolated chain, and that it can achieve volume-law entanglement even in the strong noise limit (likely persisting up to system sizes beyond the scope of classical simulation). Further, we show that the metrics which suggest classical intractability for the isolated chain point to similar conclusions in the noisy case. These results suggest that quantum sampling problems including nontrivial noise could be good candidates for demonstrating a quantum advantage in near-term hardware. |
Tuesday, March 5, 2019 3:42PM - 4:18PM |
H62.00003: Superconducting Gatemon Qubit based on a Proximitized Two-Dimensional Electron Gas Invited Speaker: Lucas Casparis The coherent tunnelling of Cooper pairs across Josephson junctions (JJs) generates a nonlinear inductance that is used extensively in quantum information processors based on superconducting circuits, from setting qubit transition frequencies and interqubit coupling strengths, to the gain of parametric amplifiers for quantum-limited readout. The inductance is either set by tailoring the metal-oxide dimensions of single JJs, or magnetically tuned by parallelizing multiple JJs in superconducting quantum interference devices (SQUIDs) with local current-biased flux lines. JJs based on superconductor-semiconductor hybrids represent a tantalizing all-electric alternative. The gatemon is a recently developed transmon variant which employs locally gated nanowire superconductor-semiconductor JJs for qubit control [1,2]. Here, we go beyond proof-of-concept and demonstrate that semiconducting channels etched from a wafer-scale two-dimensional electron gas (2DEG) are a suitable platform for building a scalable gatemon-based quantum computer [3]. We show 2DEG gatemons meet the requirements by performing voltage-controlled single qubit rotations and two-qubit swap operations. We measure qubit coherence times up to ~2 μs, limited by dielectric loss in the 2DEG host substrate. |
Tuesday, March 5, 2019 4:18PM - 4:54PM |
H62.00004: Quantum computing with driven-dissipative Josephson circuits Invited Speaker: Zaki Leghtas Superconducting qubits are one of the most promising platforms to implement quantum technologies. Quantum processors of tens of qubits are now available, and exciting applications with these intermediate size systems are in perspective. However, many algorithms, including all those with a proved quantum speed-up, require extremely low error rates. This will most likely require quantum error correction (QEC). Unfortunately, current QEC architectures require daunting overheads in physical qubits and control electronics. The goal of this research is to reduce this overhead, and our approach is based on two key ideas. First, we use high Q resonators to redundantly encode quantum information. Second, we engineer non-linear dissipation to protect and manipulate this information. |
Tuesday, March 5, 2019 4:54PM - 5:30PM |
H62.00005: A programmable superconducting quantum processor with three all-to-all coupled qubits Invited Speaker: Tanay Roy Quantum information processing (QIP) exploits the laws of quantum mechanics to enhance computational capabilities beyond the limits of classical algorithms. Among various platforms for realizing QIP, superconducting qubits are at the forefront as they offer an unparalleled combination of good coherence, fast gates, and design flexibility. A majority of recent experimental demonstrations in the superconducting architecture have utilized transmon-like qubits and transverse inter-qubit coupling for implementing small quantum algorithms. Nevertheless, efficient universal quantum computing has remained a challenge due to the limited connectivity and access to only two-qubit entangling gates. This results in reduced performance due to inefficient implementation of quantum algorithms. In this talk, I will introduce “trimon” [1], a three-qubit device based on a multi-mode superconducting circuit providing strong inter-qubit coupling and access to three-qubit native gates. I will discuss the basic working principles of the device, implementation of generalized controlled-controlled-NOT gates and universal programmability of the processor [2]. Next, I will demonstrate the high-fidelity preparation of various two- and three-qubit entangled states and implementation of a few quantum algorithms [3] like Deutsch-Jozsa, Grover's search and the quantum Fourier transform. Finally, I will talk about the possibility of scaling to larger systems using the trimon as a building block to achieve improved qubit-qubit connectivity in medium-scale quantum processors. |
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