Bulletin of the American Physical Society
APS March Meeting 2021
Volume 66, Number 1
Monday–Friday, March 15–19, 2021; Virtual; Time Zone: Central Daylight Time, USA
Session P29: Quantum Computing with Hybrid Quantum Dot SystemsLive
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Sponsoring Units: DQI Chair: Joseph Kerckhoff, HRL Laboratories, LLC |
Wednesday, March 17, 2021 3:00PM - 3:12PM Live |
P29.00001: Towards quantum simulation of spin systems using continuous variable quantum devices Razieh Annabestani, Brajesh Gupt, Bhaskar Roy Bardhan We study Bosonic representation of spin Ising model with the application of simulating two level systems using continuous variable quantum processors. We decompose the time evolution of spin systems into a sequence of continuous variable logical gates and analyze their structure. We provide an estimation of quantum circuit scaling with the size of the spin lattice system. Furthermore, we discuss the possibility of using a Gaussian Boson sampling device to estimate the ground state energy of Ising Hamiltonian. The result has potential application in developing hybrid classical-quantum algorithms such as continuous variable version of variational quantum eigensolver. |
Wednesday, March 17, 2021 3:12PM - 3:24PM Live |
P29.00002: Optimal control of the operating point of a single electron DQD coupled to a superconducting resonator Vincent Reiher, Yves Bérubé-Lauzière The single electron double quantum dot with micromagnets as described in [1] is a highly versatile architecture. Direct electrical control of gate voltages allows control of the resonant frequency of such a qubit, as well as of its magnetic dipole, through hybridization of the charge and spin degrees of freedom via a small transverse magnetic field gradient. Such a system presents three distinct operating points (OPs) of interest: |
Wednesday, March 17, 2021 3:24PM - 3:36PM Live |
P29.00003: Triplet blockade in a Josephson junction with a double quantum dot Dávid Pataki, Gorm O Steffensen, Daniel Bouman, Péter Boross, Jens Paaske, Attila Geresdi, Andras Palyi Topological superconductors are promising building blocks for future quantum computers, although their experimental realization remains a challenging task. I will present our theory results [1] on a Josephson junction with a double quantum dot. In the (1,1) charge sector of the serially coupled double quantum dot, I will illustrate a magnetically induced singlet-triplet ground-state transition via triplet blockade [2]: the Josephson current carried by the triplet ground state at high magnetic field is much suppressed compared to the current carried by the singlet ground state at low magnetic field. I will provide a simple interpretation for triplet blockade, using perturbation theory [3]. I will also present experimental data showing the triplet blockade predicted by the theory. The triplet blockade mechanism could provide a coupling mechanism between spin qubits, and superconducting qubits. |
Wednesday, March 17, 2021 3:36PM - 3:48PM Live |
P29.00004: Dual feedback squid magnetometry for sensitive spin detection Josiah Cochran, Giovanni Franco-Rivera, Lei Chen, Zhen Wang, Irinel Chiorescu Sensitive detection of spin resonance is essential for achieving coherent spin qubit control1. Recent experiments have involved bifurcation resonators2, and artificial atoms3, which provide sensitivity over a wide frequency range; however, a broadband device is needed for complex materials2. A novel differential squid detection method for spin systems on a microwave waveguide is being developed at NHMFL. This method utilizes a superconducting niobium coplanar strip line broadband microwave device coupled with niobium nano-squid devices. A nano-fabricated planar Dayem bridge squid is placed inside an omega loop for sensitive spin detection while a secondary squid is placed far away from the omega loop in order to measure background fields. The differential measurement of the fields measured by the two squids will result in a cancellation of background fields with the goal of having a more sensitive spin detection. |
Wednesday, March 17, 2021 3:48PM - 4:00PM Live |
P29.00005: Coupling silicon spin qubits via a high-impedance superconducting resonator Patrick Harvey-Collard, Guoji Zheng, Jurgen Dijkema, Tobias Bonsen, Amir Sammak, Giordano Scappucci, Lieven Vandersypen Spin qubits in silicon quantum dots are widely perceived as an ideal technology platform to realize a quantum computer. However, spins in semiconductors are not easy to couple over long distances. In this work, I will describe our experimental efforts to couple two spin qubits in Si/SiGe through a superconducting microwave resonator. To enlarge the coupling to the qubit charge dipole, we use a high-kinetic-inductance NbTiN nanowire resonator and achieve a large impedance of about 3 kΩ, resulting in a charge-resonator coupling strength gc/2π of 220 MHz and a resonator linewidth of about 2 MHz. I will demonstrate the operation of a device with two single spins, separated by 250 µm, that are resonantly coupled to the resonator simultaneously, with single-spin coupling strengths gs/2π in excess of 12 MHz. Our work opens up opportunities to adapt very powerful and well-developed techniques from circuit quantum electrodynamics and superconducting qubits to the spin qubit world. These opportunities include long-range coupling of spin qubits, and fast spin readout without local charge sensor structures. |
Wednesday, March 17, 2021 4:00PM - 4:12PM Live |
P29.00006: Realization of an Andreev spin qubit Max Hays, Valla Fatemi, Daniel Bouman, Javier Cerrillo, Spencer Diamond, Kyle Serniak, Tom Connolly, Peter Krogstrup, Jesper Nygard, Alfredo Levy Yeyati, Attila Geresdi, Michel Devoret Two promising architectures for solid-state quantum information processing are electron spins trapped in semiconductor quantum dots and the collective electromagnetic modes of superconducting circuits. Here we combine these two platforms to realize the Andreev spin qubit, the residual degree of freedom of a quasiparticle trapped in the Andreev levels of a Josephson semiconductor nanowire. The interplay between the spin-orbit coupling in the semiconductor and the superconducting-phase bias results in a spin-split spectrum without an applied Zeeman field. We demonstrate coherent spin manipulation by combining single-shot circuit QED readout and spin-flipping Raman transitions in a naturally occurring Λ system formed by the two spin states and an excited state. We measure a spin-flip time TS = 17 μs and a spin coherence time T2E = 52 ns. These results herald a new spin qubit with straightforward circuit QED integration. Moreover, they further our understanding and control of Andreev levels -- the parent states of Majorana zero modes -- in semiconductor-superconductor heterostructures. |
Wednesday, March 17, 2021 4:12PM - 4:24PM Live |
P29.00007: Electron Spin Resonance of a Gd-doped CaWO4 crystal coupled to on-chip superconducting resonators. Giovanni Franco-Rivera, Josiah Cochran, Lei Chen, Zhen Wang, Bertaina Sylvain, Irinel Chiorescu Hybrid quantum systems based on solid state spin ensembles presents as promising candidates for quantum memories due to their long coherence times1 and possibility to perform multi-state qubit operations due to their rich energy levels2. We present the coupling of coplanar stripline geometry superconducting resonator to the well-defined qubit states of Gd hosted in a CaWO4 single crystal. A number of transitions between the ground and an excited state of the electronic multiplet 8S7/2 of Gd3+ were studied by continuous-wave spectroscopy of the cavity resonance field dependence (B0 ⊥ c). Numerical calculations allowed to finely tune the high-order zero-field splitting parameters for the spin Hamiltonian at T ≈ 0.5K. |
Wednesday, March 17, 2021 4:24PM - 4:36PM Live |
P29.00008: Random-access microwave quantum memory using chirped pulse phase encoding Oscar Kennedy, James O'Sullivan, Joseph Alexander, Kamanasish Debnath, Chris Thomas, Christoph Zollitsch, Mantas Šimenas, Akel Hashim, Stafford Withington, Irfan Siddiqi, Klaus Molmer, John J. L. Morton We introduce a random access quantum memory protocol using adiabatic fast passages (AFPs) to imprint phase shifts onto single quantum excitations stored in an ensemble of emitters coupled to a cavity. These spatially- and spectrally-dependent phase shifts suppress collective emission of the excitations stored in the ensemble and uniquely label them so they can be retrieved on-demand following the application of a precise AFP. In addition to random access, our protocol offers in-built dynamical decoupling while suppressing emission into the cavity when the ensemble is in the excited state. We experimentally demonstrate the protocol using Bi donor spins in Si coupled to a superconducting resonator, storing up to four weak (~400 photon) microwave pulses before retrieving them, in a different order, up to 2 ms later. With even modest cooperativity (C~0.05) echo emission from the excited ensemble state results in superradiant echo emission, reducing the fidelity and lifetime of the memory, and we show that this is mitigated using our protocol. Finally, we explore the independence of the storage modes and implications for scaling the memory and enhancing its efficiency and lifetime. |
Wednesday, March 17, 2021 4:36PM - 4:48PM Live |
P29.00009: Microscopic bath effects on noise spectra in semiconductor quantum dot qubits Jason Kestner, Seongjin Ahn When a system is thermally coupled to only a small part of a larger bath, statistical fluctuations of the temperature (more precisely, the internal energy) of this "sub-bath" around the mean temperature defined by the larger bath can become significant. We show that these temperature fluctuations generally give rise to 1/f-like noise power spectral density from even a single two-level system. We extend these results to a distribution of fluctuators, finding the corresponding modification to the Dutta-Horn relation. Then we consider the specific situation of charge noise in silicon quantum dot qubits and show that recent experimental data can be modeled as arising from as few as two two-level fluctuators, and accounting for sub-bath size improves the quality of the fit. |
Wednesday, March 17, 2021 4:48PM - 5:00PM Live |
P29.00010: Narrow linewidth tin-vacancy centers in diamond waveguides Alison Rugar, Shahriar Aghaeimeibodi, Constantin Dory, Haiyu Lu, Patrick J McQuade, Sattwik Mishra, Shuo Sun, Zhixun Shen, Nicholas A Melosh, Jelena Vuckovic Coupling high-quality solid-state quantum emitters to photonic devices is a critical step towards building quantum photonic networks. The negatively charged tin-vacancy (SnV-) center in diamond is a promising optically accessible solid-state qubit candidate with narrow-linewidth emission and long spin coherence time. However, the integration of SnV- centers into photonic devices has yet to be realized. In this talk, we present narrow-linewidth SnV- centers (~36 MHz) in diamond waveguides [ACS Photonics 7, 2356-2361 (2020).]. We use our recently developed shallow ion implantation and growth technique to generate SnV- centers and apply the quasi-isotropic etch technique to fabricate suspended diamond nanostructures. |
Wednesday, March 17, 2021 5:00PM - 5:12PM Live |
P29.00011: Characterization of superconducting transport in CMOS PtSi transistors for scalable qubits Tom Vethaak, Laurie E. Calvet, John P. Snyder, François Lefloch Scalability in fabrication and operation is key to move beyond the NISQ era. So far, superconducting transmon qubits, based on aluminum tunnel Josephson junctions, have demonstrated the most advanced achievements. However, this technology is difficult to use at large scale. Recently, an alternative "gatemon” has appeared using hybrid superconducting/semiconducting (S/Sm) nano-devices as gate-tuned Josephson junctions. Current implementations use nanowires, of which the large-scale fabrication has not yet matured. CMOS Josephson Field-Effect Transistors may be used instead as tunable weak link in a scalable gatemon design. |
Wednesday, March 17, 2021 5:12PM - 5:24PM Live |
P29.00012: Optimizing the density of delta doped Al in Si toward superconductivity Ke Tang, Hyun Kim, Aruna N Ramanayaka, Joshua Pomeroy Potential superconductivity in heavily delta-doped Al in Si, with a predicted Tc ≈ 6 K, would be an attractive candidate for bridging superconducting QIS with silicon-based quantum devices for a new generation of solid-state quantum computing. In this talk, we present the material properties and electrical characterization of our 2nd generation super-saturated Al delta doped layers. Solid phase epitaxy recovery (SPER) with an improved incorporation anneal are conducted during material synthesis followed by fabrication of mesa-etched hall bars to study the carrier density, mobility and temperature dependence of these properties. So far, a maximum 2D density of 3.2x1014 cm-2 with dopant activation close to 100% has been achieved, doubling the density compared to our 1st generation delta layer. Secondary ion mass spectroscopy (SIMS), scanning tunneling microscopy and magneto-transport results are all presented to compare the impact of different growth processes on dopant diffusion and segregation in Si. |
Wednesday, March 17, 2021 5:24PM - 5:36PM Live |
P29.00013: Applications of InAs-Al Heterostructures in Quantum Computing Joseph Yuan, William Strickland, Matthieu Dartiailh, Joshua Tong, Mehdi Hatefipour, Kaushini S Wickramasinghe, Fatemeh Barati, Kasra Sardashti, Javad Shabani Josephson junctions created from Indium Arsenide (InAs) and Aluminum (Al) heterostructures allow for the integration of tunable superconductivity into microwave circuits. Superconducting circuits used for quantum computation can benefit from these type of elements in a variety of ways. In our group we have demonstrated how a highly transparent contact between a superconductor and a semiconductor allows a two dimensional electron gas in a layer of InAs to be proximitized by superconducting Al [1]. The 2DEG is gate voltage tunable. By using a simple gate electrode the carrier density of the 2DEG can be adjusted and consequently adjust the amount of supercurrent allowed to pass through the junction. This circuit element has been used to create a gate tunable modified transmon dubbed a gatemon [2]. Here we explore gatemon qubits and other use cases such as tunable resonators, tunable bus couplers and in general the use of InAs-Al heterostructures for superconducting circuits in the realm of quantum computing. |
Wednesday, March 17, 2021 5:36PM - 5:48PM Live |
P29.00014: Optimizing magnetic dopants in ferroelectrics for defect-based qubits Katherine Inzani, Weichuan Huang, Junjie Liu, Valentin V. Laguta, Sujit Das, Ruchira Chatterjee, Nima Leclerc, Evan Sheridan, Arzhang Ardavan, Ramamoorthy Ramesh, Sinéad Majella Griffin Introducing magnetic dopants to ferroelectric crystals provides unpaired spins with coupled electrical and magnetic properties that could be utilized in a novel spin-oxide qubit platform. Depending on the symmetry of the ferroelectric host, the spins preferentially align relative to the polar axis and follow manipulation of the polar axis by an applied electric field. We demonstrate this electric-field control by a combined first-principles and electron paramagnetic resonance study of the model system Fe3+-doped PbTiO3. We further explore ferroelectric oxide systems with reduced symmetry, alternative dopants and lattice modifications to optimize the magnetoelectric coupling and understand spin-lattice decoherence channels. These results demonstrate the manipulation of spins by an electric field and the options available for optimizing spin control by tailoring the atomic environment. |
Wednesday, March 17, 2021 5:48PM - 6:00PM Live |
P29.00015: N-qubit entanglement of encoded qubits via curvature couplings to a superconducting cavity and joint continuous measurement Rusko Ruskov, Charles Tahan We propose entangling preparation procedures based on curvature couplings of encoded qubits to a superconducting (SC) cavity, exploring the non-linear qubit response. The proposed scheme allows |
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