Bulletin of the American Physical Society
APS March Meeting 2019
Volume 64, Number 2
Monday–Friday, March 4–8, 2019; Boston, Massachusetts
Session C35: Hybrid Systems: Coupling Spin Qubits with Microwave ResonatorsFocus
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Sponsoring Units: DQI Chair: Vanita Srinivasa, Sandia National Laboratories Room: BCEC 205B |
Monday, March 4, 2019 2:30PM - 3:06PM |
C35.00001: Circuit Quantum Electrodynamics with superconductor-semiconductor hybrid systems Invited Speaker: Pasquale Scarlino Semiconductor qubits rely on the control of charge and spin degrees of freedom of electrons or holes confined in quantum dots (QDs). Typically, semiconductor qubit-qubit coupling is short range, effectively limiting qubit distance to the spatial extent of the wavefunction of the confined particle (a few hundred nanometers). This is a significant constraint towards scaling of QD-based architectures to realize dense 1D or 2D arrays of QDs. Inspired by techniques originally developed for circuit QED, we recently demonstrated the strong coupling of individual electrons [1,2] confined in GaAs quantum dots to individual microwave photons, making use of the enhanced electric component of the vacuum fluctuations of a resonator with impedance beyond the typical 50 Ohm of standard coplanar waveguides. In this hybrid technology, we recently realized a proof of concept experiment, where the coupling between a transmon and a double QD (DQD) is mediated by virtual microwave photon excitations in a high impedance SQUID array resonator, which acts as a quantum bus enabling long-range coupling between dissimilar qubits [3]. Similarly, we achieved coherent coupling between two DQD charge qubits separated by approximately 50 um [4]. In the dispersive regime, we spectroscopically observed qubit-qubit coupling as an avoided-crossing in the energy spectrum of the DQD charge qubits. The methods and techniques developed in this work are transferable to QD devices based on other material systems and can be beneficial for spin based hybrid systems [5]. |
Monday, March 4, 2019 3:06PM - 3:18PM |
C35.00002: Towards cavity-mediated coupling of spin-qubits Felix Borjans, Xanthe Croot, Xiao Mi, Jason R Petta While single-qubit gates with fidelities approaching superconducting qubits have been demonstrated [1] and two-qubit gates based on nearest-neighbour exchange are being realized with improving performance on length scales of a few hundred nanometers [2-4], cavity-mediated coupling of spin-qubits over ~1 cm distances remains an outstanding challenge. With the recent demonstration of strong-coupling of a single electron-spin to the electric field of a cavity photon [5, 6], this long-range entanglement between two spin-qubits is within reach. Here we present recent progress in our effort to complete this milestone. |
Monday, March 4, 2019 3:18PM - 3:30PM |
C35.00003: Multi-qubit entangling gates for spins in silicon Michael Gullans, Jason R Petta Implementing large-scale algorithms on a quantum computer will require efficient gate compilation strategies to reduce overhead. We recently demonstrated an efficient CNOT gate for spins in Si [1]. The gate operates in a regime where the magnetic field gradient exceeds exchange. By turning on exchange, it is possible to implement a CNOT gate in a single step using resonant microwave excitation. We will discuss possible extensions of the resonant gate in more complex device architectures [2] and present a detailed analysis of multi-qubit gate fidelities. |
Monday, March 4, 2019 3:30PM - 3:42PM |
C35.00004: Using magnetically-resilient circuit QED techniques to study 2D materials Charlotte Boettcher, Uri Vool, Yinyu Liu, Joel Wang, Greg Calusine, David K Kim, Danna Rosenberg, Jonilyn L Yoder, Amir Yacoby, William D Oliver Combining superconducting circuits with materials hosting exotic quantum properties to create hybrid circuits allows us to utilize circuit QED techniques to measure such materials. This new platform requires development of superconducting resonators that can sustain a high quality factor even in presence of an applied magnetic field, often required to access novel quantum effects in such materials. |
Monday, March 4, 2019 3:42PM - 3:54PM |
C35.00005: Design of Multi-chip Module with High Impedance Microwave Resonators for cQED Experiments with Si/SiGe Quantum Dots Nathan Holman, Danna Rosenberg, Jonilyn Yoder, William D. Oliver, Matthew A Beck, Robert F McDermott, Mark G Friesen, Susan Coppersmith, Mark Alan Eriksson Recent work coupling semiconductor qubits to resonators has shown that the use of high kinetic inductance resonators aids in the achievement of strong coupling [1]. We present the design of a multichip module consisting of a Si/SiGe quantum dot die bump-bonded to a TiN superconducting resonator die. This process allows for separate optimization of each circuit component. To increase the resonator impedance, we use TiN which allows for increased kinetic inductance in the superconducting film. Using finite element simulation of the 3D structure and experimentally extracted inductances we target a nominal design impedance of 250-400 ohms for a 100 nm thick film within constraints of the resonator fabrication. |
Monday, March 4, 2019 3:54PM - 4:06PM |
C35.00006: Integrating singlet-triplet qubits with superconducting resonators Shannon Harvey, Charlotte Boettcher, Saeed Fallahi, Michael Manfra, Amir Yacoby Singlet-triplet qubits possess many appealing traits for building a quantum computer, in large part because they have reduced coupling to charge yet retain fast single-qubit gate speeds. While they are limited by their slow and short range two-qubit gate, incorporating superconducting resonators into the singlet-triplet qubit architecture shows promise for alleviating both issues. However, the singlet-triplet qubit is extremely sensitive to changes in its electrostatic environment, which can be affected both by the fabrication process for the resonator and by the presence of the proximal resonator gate. Moreover, because the singlet-triplet qubit has reduced coupling to charge, achieving high-fidelity gates requires a high-impedance resonator, which carries unique fabrication constraints. In my talk, I will discuss measurements we have done to study and quantify the impacts of these changes, as well as techniques we have developed to mitigate any negative effects. |
Monday, March 4, 2019 4:06PM - 4:18PM |
C35.00007: Understanding curvature (quantum capacitance) couplings of spin qubits to a superconducting cavity as a low-energy limit Rusko Ruskov, Charles Tahan We describe in a general perturbation theory approach the origin of the couplings of a spin qubit to a superconducting (electromagnetic) cavity. Special attention is paid to the so-called curvature couplings related to qubit’s quantum capacitance, which is derived as a low-energy limit of a perturbation expansion to second order. We discuss the applicability of these couplings to current experiments with multi-dot spin-qubits, including single-, double, and triple-quantum dot qubits, as well as with superconducting qubits. |
Monday, March 4, 2019 4:18PM - 4:30PM |
C35.00008: Exploring the sweet-spot regime of singlet-triplet qubits coupled to a microwave resonator Jose Carlos Abadillo-Uriel, Mark Alan Eriksson, Susan Coppersmith, Mark G Friesen Singlet-triplet S-T0 qubits are robust against global magnetic noise and, at the symmetric operating point, charge fluctuations [4]. However, strong coupling to a resonator requires hybridizing the (1,1) and (0,2) singlet states, making the qubit more sensitive to charge noise. We find that, in the operating regime where the tunnel coupling is comparable to the magnetic field gradient, sweet spots emerge, that are distinct from the symmetric operating point, but offer interesting opportunities for high-fidelity gate operations. |
Monday, March 4, 2019 4:30PM - 4:42PM |
C35.00009: Two-qubit gates between quantum dot spins coupled by a resonator Ada Warren, Edwin Barnes, Sophia Economou Recent experimental work with silicon qubits has shown that it is possible, using an inhomogeneous magnetic field, to strongly couple the modes of a superconducting resonator to the spin of a single electron trapped within a double quantum dot. This suggests the possibility of realizing long-range spin-spin interactions mediated by cavity photons. We present here our theoretical calculation of the effective interaction between distant quantum dot spins coupled via a resonator and our proposed cavity-mediated two-qubit gate. |
Monday, March 4, 2019 4:42PM - 4:54PM |
C35.00010: Highly coherent spin states in carbon nanotubes coupled to cavity photons Tino Cubaynes, Matthieu Delbecq, Matthieu Dartiailh, Réouven Assouly, Matthieu M Desjardins, Lauriane Contamin, Laure Bruhat, Zaki Leghtas, Francois Mallet, Audrey Cottet, Takis Kontos Circuit quantum electrodynamics allows one to probe, manipulate and couple superconducting quantum bits using cavity photons at an exquisite level. Mesoscopic-QED inherits the c-QED toolbox and applies it to quantum dot circuits. In this talk, I will present a spin-qubit encoded in a carbon nanotube based double quantum dot with non-collinear ferromagnetic contacts. Using the c-QED spin-photon interface, we drove a single electronic spin and performed microwave spectroscopy of it. From this measurement we identified a decay rate which can be tuned to be as low as 250kHz. The cooperativity of the spin-photon interface is also measured as a function of the detuning, allowing to identify an optimal working point. These coherence properties, which are attributed to the use of pristine carbon nanotubes stapled inside the cavity, should enable coherent spin-spin interaction via cavity photons and compare favorably to the ones recently demonstrated in Si-based circuit QED experiments. |
Monday, March 4, 2019 4:54PM - 5:06PM |
C35.00011: Magnon-photon coupling between a superconducting resonator and a thin film permalloy stripe Yi Li, Tomas Polakovic, Yonglei Wang, Jing Xu, Sergi Lendinez, Zhizhi Zhang, Junjia Ding, Trupti Khaire, Hilal Saglam, Ralu Divan, JOHN E. PEARSON, Wai-Kwong Kwok, Zhili Xiao, Valentyn Novosad, Axel F Hoffmann, Wei Zhang Coherent processing of magnetic excitations has received increasing attentions for spin-wave-based functionality such as magnonics, cavity spintronics and quantum information processing. They usually involve strong coupling of different excitations, such as magnons and photons, which leads to their hybridized modes. |
Monday, March 4, 2019 5:06PM - 5:18PM |
C35.00012: Long-distance coherent coupling of a spin qubit to a superconducting qubit Andreas Landig, Jonne Koski, Pasquale Scarlino, David Van Woerkom, Christian Reichl, Werner Wegscheider, Andreas Wallraff, Klaus Ensslin, Thomas Ihn A coherent link connecting different qubits over long distances is necessary to benefit from the advantages in gating or coherence times of different qubit implementations in a future quantum processor. We realize such a link between a spin qubit and a transmon qubit in a circuit quantum electrodynamics architecture [1] similar to a recent work that involved a charge qubit and a transmon qubit [2]. The spin qubit is a resonant exchange qubit [3] formed by three electrons in a gate defined triple quantum dot in a GaAs/AlGaAs heterostructure. The qubit states are split energetically by exchange interaction. Consequently, the spin qubit can be operated at zero magnetic field and exhibits a decoherence rate of γ2/2π≈10MHz, limited by hyperfine interaction in the host material. The transmon qubit has γ2/2π≈0.7MHz limited by Purcell decay. Both qubits are capacitively coupled to a high impedance SQUID array resonator with coupling strengths of gSQ/2π≈50MHz and gT/2π≈180MHz for the spin and transmon qubit, respectively. We demonstrate resonant and dispersive interaction between the two qubits mediated by real and virtual microwave photons. |
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