Bulletin of the American Physical Society
APS March Meeting 2020
Volume 65, Number 1
Monday–Friday, March 2–6, 2020; Denver, Colorado
Session S16: Multi-mode and 3D-cavity Circuit QED Systems II |
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Sponsoring Units: DQI Chair: Yvonne Gao, Natl Univ of Singapore Room: 201 |
Thursday, March 5, 2020 11:15AM - 11:27AM |
S16.00001: Mediating interactions between superconducting microwave cavities with three-wave mixing, part 1 Stijn de Graaf, Benjamin Chapman, Yaxing Zhang, Shantanu O Mundhada, Akshay Koottandavida, Nicholas Frattini, Luke Burkhart, Alexander P Read, Luigi Frunzio, Steven Girvin, Michel H. Devoret, Robert Schoelkopf Engineering tunable bilinear couplings between microwave cavities provides a way to manipulate and entangle long-lived quantum states. Two-cavity gates, such as the beam splitter and exponential SWAP (eSWAP), have been successfully demonstrated using a driven transmon coupled to both cavities. However, the fidelity of these gates is limited by unwanted 4th order processes such as the AC Stark effect. By replacing the transmon’s Josephson junction with a superconducting nonlinear asymmetric inductive element (SNAIL), we produce a bilinear interaction via its 3rd order nonlinearity while minimizing 4th order effects. This is expected to offer high fidelity two-cavity gates using all-RF control. I will discuss experimental design considerations and the theory behind the coupled-cavity device. |
Thursday, March 5, 2020 11:27AM - 11:39AM |
S16.00002: Mediating interactions between superconducting microwave cavities with three-wave mixing, part 2 Benjamin Chapman, Stijn de Graaf, Yaxing Zhang, Shantanu O Mundhada, Akshay Koottandavida, Nicholas Frattini, Luke Burkhart, Alexander P Read, Luigi Frunzio, Steven Girvin, Michel H. Devoret, Robert Schoelkopf Quantum memories formed from three-dimensional superconducting microwave cavities provide the coherence and large Hilbert spaces needed for quantum error correction. To date, coupling between these memories has been primarily facilitated by transmons. There, four-wave mixing allows for the creation of beam-splitter, single-mode, and two-mode-squeezing interactions, from which gates can be built. Although this approach has proven to be flexible and robust, the engineered couplings are accompanied by unwanted Kerr and Stark effects, which can limit the fidelity of cavity-cavity gates. Here, we design the nonlinear coupling element to be an RF-driven three-wave mixer. The desired bilinear interactions may then be engineered while suppressing spurious fourth-order processes. In this talk, we present preliminary measurements of two microwave cavities coupled by such a three-wave mixing element. |
Thursday, March 5, 2020 11:39AM - 11:51AM |
S16.00003: Superconducting radio frequency cavities with seconds of photon lifetime in quantum regime Alexander Romanenko, Roman Pilipenko, Daniil Frolov, Silvia Zorzetti, Mohamed Awida, Sam Posen, Eric T Holland, Sergey A Belomestnykh, Anna Grassellino Superconducting radio frequency (SRF) cavities developed for accelerators are the highest quality factor (Q) man-made oscillators with record Q > 4e11, whereas Q~3e10 is a routine operation. Adopted for quantum regime, SRF cavities offer a route for multifold increase in photon lifetimes for applications in quantum computing and fundamental physics searches such as dark photons and axions. Initial demonstrations showed that the quantum regime lifetimes of tens of milliseconds can be achieved for SRF cavities "as-is", limited by the two-level-system (TLS) dissipation [1,2]. |
Thursday, March 5, 2020 11:51AM - 12:03PM |
S16.00004: Exploiting tunable, ultrastrong nonlinearies of the cavity Cooper-pair transistor system for generating microwave quantum states William Braasch, Miles Blencowe, Oscar D. Friedman, Andrew D. Armour, Benjamin Brock, Alexander J Rimberg The cavity Cooper-pair transistor (cCPT) device enables the engineering of a wide range of non-linear, effective cavity oscillator interactions through the tunability of both its gate voltage and flux biases. Such nonlinearities can be strong even under low average photon number drives on the cavity. We utilize the recently developed Wigner current vector field (Wigner current) construct to give a geometrical analysis of the formation and possible stabilization of quantum microwave oscillator states in the presence of dissipation and noise for the cCPT. |
Thursday, March 5, 2020 12:03PM - 12:15PM |
S16.00005: Passive Error Correction with Grid States in a Non-Reciprocal Superconducting Circuit Martin Rymarz, Stefano Bosco, Alessandro Ciani, David Peter DiVincenzo Non-reciprocal circuit elements play an essential role for the practical realization of a solid-state quantum computer, independent of the chosen implementation. For that matter, non-reciprocal circuit elements often constitute the interface between the classical and quantum description of an electrical network. |
Thursday, March 5, 2020 12:15PM - 12:27PM |
S16.00006: Cat-qubit operations preserving error structure Jonathan Gross, Shruti Puri, Alexandre Blais A universal quantum computer will require error correction to perform in a fault-tolerant way, imposing substantial engineering challenges. Fortunately, many devices are subject to errors with structure that can be exploited to ease the burden of fault tolerance. Stabilized cat qubits in superconducting circuits push this principle to the extreme, with recent work identifying dramatic reduction of fault-tolerance requirements on this platform. Essential to this reduction is the ability to perform operations on the qubits that preserve the error structure, made possible by the infinite-dimensional Hilbert space in which the cats live. We present additional operations fulfilling this requirement and discuss their potential for near- and long-term applications. |
Thursday, March 5, 2020 12:27PM - 1:03PM |
S16.00007: Multiplexed Readout of Four Qubits in 3D cQED Architecture Using Broadband JPA Invited Speaker: R Vijay We propose and demonstrate a frequency-multiplexed readout scheme in 3D cQED architecture. We use four transmon qubits coupled to individual rectangular cavities which are aperture-coupled to a common rectangular waveguide feedline. A coaxial to waveguide transformer at the other end of the feedline allows one to launch and collect the multiplexed signal. The reflected readout signal is amplified by an impedance engineered broadband parametric amplifier with 380 MHz of bandwidth. This provides us high fidelity single-shot readout of multiple qubits using compact microwave circuitry, an efficient way for scaling up to more qubits in 3D cQED. I conclude the talk by discussing some latest results on a new type of qubit-cavity system measured using a 3D waveguide. |
Thursday, March 5, 2020 1:03PM - 1:15PM |
S16.00008: Waveguide Bandgap Engineering with an Array of Superconducting Qubits Jan Brehm, Alexander Stehli, Alexander N. Poddubny, Tim Wolz, Hannes Rotzinger, Alexey V. Ustinov The interaction of qubits with free space instead of a cavity gives rise to several effects, which could play an important role for the implementation of a quantum computer. One of the most intriguing features is that in one-dimensional free space the interaction between qubits is of infinite range and can be tuned by varying the qubit separation [1]. In this work, we experimentally study an array of eight superconducting transmon qubits with local frequency control, which are all coupled to the mode continuum of a superconducting waveguide. The spacing between adjacent qubits is substantially smaller than the wavelength corresponding to their excitation frequency, eliminating almost completely the coherent exchange type interaction between qubits. By consecutively tuning the qubits to a common resonance frequency we observe the formation of super- and subradiant states as well as the emergence of a bandgap. Making use of the anharmonic level structure of the transmon qubit we study the nonlinear saturation of the collective modes with increasing photon number and electromagnetically induce a transparency window in the bandgap region of the ensemble. |
Thursday, March 5, 2020 1:15PM - 1:27PM |
S16.00009: Quantum impurity simulation in a photonic crystal with superconducting circuits Andrei Vrajitoarea, Ron Belyansky, Rex Lundgren, Seth P Whitsitt, Alexey V Gorshkov, Andrew Houck Superconducting circuits have emerged as a rich platform for emulating synthetic materials composed of artificial atoms and photonic lattices. Here, we apply this toolbox for exploring the physics of a quantum impurity coupled to a photonic crystal. In previous experiments, strongly coupling a transmon qubit to the band structure of a stepped impedance waveguide filter has led to the first observation of atom-photon dressed bound states. In this work, we push the coupling strength even further to go beyond the single-photon limit. Our platform consists of a photonic crystal implemented as a linear array of 26 coupled microwave resonators, and a fluxonium qubit galvanically coupled to one resonator site. Tuning the coupling strength, we can reach a regime where counterrotating terms become relevant and multiphoton bound states participate in the single-photon scattering dynamics. Additionally, by probing the transmission response for each discrete bath mode subject to a qubit drive, we can extract the spin-bath susceptibilities that capture the many-body correlations between the impurity and the harmonic degrees of freedom in the crystal. |
Thursday, March 5, 2020 1:27PM - 1:39PM |
S16.00010: High coherence bosonic modes in long Josephson junction chains Nitish Jitendrakumar Mehta, Roman Kuzmin, Nicholas Grabon, Vladimir Manucharyan Owing to high coherence and easy fabrication, 3-D Superconducting microwave cavities coupled to ancilla qubits are an attractive platform for the storage and manipulation of continuous variable quantum information. Recent experiments have demonstrated high fidelity QND readout, arbitrary control and remote entanglement of photonic states in these cavities[1]. Despite the progress, large size of the 3-D cavities poses a significant hurdle in scaling up the architecture. Here we present a way to get around the problem by using standing wave modes in 6mm long transmission line made out of two parallel chains of Josephson junctions[2]. Remarkably, we measure energy relaxation times exceeding 1ms in a setup with more than 20,000 junctions in one device. |
Thursday, March 5, 2020 1:39PM - 1:51PM |
S16.00011: Experimental Realization of the bosonic Kitaev-Majorana model Jimmy Shih-Chun Hung, J. Busnaina, M.V. Moghaddam, Chung Wai Sandbo Chang, Ananthapadmanabha Vadiraj, C.M. Wilson Superconducting quantum circuits (SQC) are a natural platform for quantum simulations of a wide variety of important lattice models, spanning condensed matter to high-energy physics. The varied toolbox of SQC allow the simulation of a variety of phenomena, including topological effects. Recently, McDonald et al proposed one such topological model that they dubbed the bosonic Kitaev-Majorana model. The model is a bosonic analog of the well-known fermionic Kitaev-Majorana model that has garnered great interest recently. Both models consist of a 1D chain connected by a hopping term but also subject to a pairing potential for the resident excitations. While the bosonic model does not reproduce all of the features of the original, it still exhibits a number of interesting topological features, such as chiral transport. Here we implement the bosonic Kitaev-Majorana model using a multimode superconducting parametric cavity. The nodes of the lattice are mapped to frequency modes of the cavity. The complex hopping terms are created by parametric pumping at mode-difference frequencies, while the pairing potential is induced by pumping at mode-sum frequencies. We present results for simulations on small lattices and discuss possibilities for scaling up the lattice size. |
Thursday, March 5, 2020 1:51PM - 2:03PM |
S16.00012: Driven quantum nonlinear resonators: new exact solution techniques and generalized photon blockade David Roberts, Aashish Clerk Interacting driven-dissipative quantum resonators are at the forefront of research in quantum optics and quantum computing with superconducting circuits. We develop a new theoretical approach that allows one to non-perturbatively find the steady states of such systems. Our approach uncovers surprising phenomena in systems with an unusual three-photon coherent drive. This includes a new kind of generalized photon blockade effect, where interference causes a sharp cut-off in the system’s photon-number distribution despite without requiring extremely strong nonlinearity. This is distinct from standard photon blockade (which requires a strong nonlinearity), or the so-called “unconventional photon blockade” (which does not completely suppress high photon number states). We also describe a new kind of quantum bistability in these systems, which we can understand as a kind of interference between pairs of holomorphic functions in phase space. The effects we describe are well within the reach of current experiments in circuit QED, and could be harnessed for a variety of applications in quantum information processing. |
Thursday, March 5, 2020 2:03PM - 2:15PM |
S16.00013: Encoding qubits in Bloch states of superconducting devices Thomas Stace, Arne Grimsmo, Clemens Mueller, Jared H. Cole, Dat Thanh Le We describe two related superconducting circuits, the transmon [1] and the dualmon [2] in terms of Bloch states that reflect periodic symmetries in their Hamiltonians. We use these two systems to illustrate a new scheme for encoding a qubit into superconducting qubits, using states in the lowest Bloch band. We discuss how these states are likely to be extremely robust against relaxation and noise, and suggest possible gates for controlling the state of such systems. |
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