Bulletin of the American Physical Society
APS March Meeting 2017
Volume 62, Number 4
Monday–Friday, March 13–17, 2017; New Orleans, Louisiana
Session V52: Hybrid Systems with Semiconductor QubitsFocus

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Sponsoring Units: GQI Chair: Vanita Srinivasa, Sandia National Laboratories Room: 399 
Thursday, March 16, 2017 2:30PM  3:06PM 
V52.00001: Coupling of threespin qubits to microwave cavities Invited Speaker: Maximilian Russ Qubit cavity coupling and hybrid quantum systems are recently under intense investigation due to its application in longdistance entanglement protocols and fast quantumstate readout schemes. We investigate the behavior of qubits consisting of three electron spins in triple quantum dots (TQDs) which are coupled to a microwave cavity via their electric dipole moment\footnote{M. Russ, F. Ginzel, and G. Burkard, Phys. Rev. B 94, 165411 (2016)}. Our model includes two different geometries of the hybrid where the qubit is embedded longitudinally or transversally inside the cavity which yield a qubitcavity coupling to independent TQD detuning parameters, $\varepsilon$ and $\varepsilon_{M}$. These parameters can be controlled in experiments by gate voltages applied to the quantum dot structures. By varying the detuning parameters, one can switch the qubit type from the resonant exchange qubit to other threespin qubit encodings by shifting the energies in the single quantum dots thus changing the electron occupancy in each. In a semimicroscopic approach we calculate the transition dipole matrix elements of the qubitcavity interaction that determine the qubitcavity coupling strength needed for twoqubit gates and dispersive readout\footnote{G. Burkard and J. Petta, arXiv:1607.08801 (accepted in Phys. Rev. B, 2016)}. We investigate both geometries and compare the two with and without the influence of charge noise. As a final result, the requirements for the vacuum coupling strength and quality factor of the cavity are presented. [Preview Abstract] 
Thursday, March 16, 2017 3:06PM  3:18PM 
V52.00002: Strong coupling in cavity QED with quantum dot circuits Matthieu Dartiailh, Laure Bruhat, Tino Cubaynes, Jeremy Viennot, Matthieu Desjardins, Audrey Cottet, Takis Kontos Cavity quantum electrodynamics techniques have turned out to be instrumental to probe or manipulate the electronic states of nanoscale circuits. Recently, cavity QED architectures have been extended to quantum dot circuits. These circuits are appealing since other degrees of freedom than the traditional ones (e.g. those of superconducting circuits) can be investigated. We will show how one can use carbon nanotube based quantum dots in that context. In particular, we demonstrate a superconductorquantum dot circuit which realizes the strong coupling of an individual electronic excitation to microwave photons. The vacuum Rabi splitting 2g~10 MHz exceeds by a factor of 3 the linewidth of the hybridized lightmatter states. Our findings open the path to ultralong distance entanglement of quantum dot based qubits. [Preview Abstract] 
Thursday, March 16, 2017 3:18PM  3:30PM 
V52.00003: Coupling a SQUID array resonator with a semiconductor charge qubit Anna Stockklauser, Pasquale Scarlino, Jonne Koski, Simone Gasparinetti, Anton Potocnik, Christian Reichl, Werner Wegscheider, Thomas Ihn, Klaus Ensslin, Andreas Wallraff Strong coupling between superconducting artificial atoms and coplanar waveguide resonators is routinely achieved in circuit QED. Coupling rates to gate defined semiconductor quantum dots are so far limited to about 50 MHz [1], due to their smaller dipole moment. By increasing the characteristic impedance of the resonator, it is possible to enhance the zero point voltage fluctuations, thus improving the electric dipole coupling to qubits. We aim to couple a semiconductor double quantum dot with a high impedance superconducting resonator realized using a SQUID array resonator of 1.5 k$\Omega$ impedance and an internal quality factor of up to $10^4$. Considering a charge qubit decoherence rate of roughly 250 MHz, reported in [2], the coupling achievable with this kind of resonators is expected to be sufficient to reach the strong coupling regime. \newline [1] T.~Frey {\em et al.}, Phys.~Rev.~Lett.~{\bf 108}, 046807 (2012).\newline [2] A.~Stockklauser {\em et al.}, Phys.~Rev.~Lett.~{\bf 115}, 046802 (2015).\newline [Preview Abstract] 
Thursday, March 16, 2017 3:30PM  3:42PM 
V52.00004: High impedance lumped element nanoresonators for quantum dot circuit quantum electrodynamics S. Putz, F. Borjans, X. Mi, J. R. Petta The strength of vacuum voltage fluctuations in an $LC$ circuit is proportional to its impedance $Z$. Therefore, increasing the impedance of superconducting resonators well above the standard impedance of $Z = 50~\Omega$ will allow for increased coupling rates between cavity photons and single electrons in gate defined quantum dots. Alternative to using ultra high kinetic inductance materials and distributed circuits to achieve high impedance\footnote{N. Samkharadze \textit{et al.}, Phys. Rev. Applied \textbf{5}, 044004 (2016)}, I will present a new approach based on planar lumped element nanoresonators. The presented devices consist of nanowires fabricated from a 15 nm thick Nb film that is sputtered onto high resistivity silicon. The nanoresonators with $Z\sim1$ k$\Omega$ enable the versatile design of multiqubit arrays coupled to a single mode cavity. [Preview Abstract] 
Thursday, March 16, 2017 3:42PM  3:54PM 
V52.00005: Prospective enhancement in the spintophoton magnetic coupling rate using trilayer lumpedelement superconducting resonators Bahman Sarabi, Peihao Huang, Neil Zimmerman Siliconbased singleatom spin qubits currently hold the record coherence times of any single qubit in the solid state. However, there are challenges in direct magnetic coupling of an electron spin to other systems such as microwave photons. This is due the relatively small magnetic moment of the electronic spin, and the relatively weak magnetic field of quantum circuits at typical drive powers. Therefore, direct magnetic coupling usually offers insufficient spin rotation speeds and readout fidelities for practical qubit applications. To enhance the direct magnetic coupling to the spin, we propose a device consisting of a trilayer lumpedelement superconducting resonator and a single donor implanted in enriched $^{28}$Si. The resonator, in contrast to coplanar waveguide resonators, includes a nanoscale spiral inductor to spatially focus the magnetic field from the photons within. The design promises approximately two orders of magnitude increase in the local magnetic field, and thus the spin to photon coupling rate $g$, compared to the estimated coupling rate to coplanar transmissionline resonators. This relatively large $g$ can lead to significant improvements in the initialization time, spin rotation speed and readout fidelity of singleatom spin qubits. [Preview Abstract] 
Thursday, March 16, 2017 3:54PM  4:06PM 
V52.00006: Quantumlimited measurement and gates on spin qubits via curvature coupling to cavity Rusko Ruskov, Charles Tahan We have studied the possibility of a coupling of encoded quantum dot spinqubit to a microwave resonator via the qubit energy level curvature and gate voltage variation (both quantum and classical). A coupling strength of tens of MHz can be achieved both with/without external voltage modulation, while minimizing charge dephasing and avoiding enhanced decoherence (Purcell) effect. We investigated specific procedures for selective qubit(s) readout, switching on/off the coupling, with the prospect for quantumlimited qubit(s) measurement for generating qubit entanglement. Implications of the curvature couplings for geometric quantum gates on spin qubits are also considered. [Preview Abstract] 
Thursday, March 16, 2017 4:06PM  4:18PM 
V52.00007: Coupling a single electron spin to a microwave resonator: Part I: controlling transverse and longitudinal couplings Dany LachanceQuirion, F\'{e}lix Beaudoin, Julien Camirand Lemyre, William A. Coish, Michel PioroLadri\`{e}re Novel quantum technologies can be combined within hybrid systems to benefit from the complementary capabilities of individual components. For example, microwavefrequency superconducting resonators are ideally suited to perform qubit readout and to mediate twoqubit gates, while spin qubits offer long coherence times and highfidelity singlequbit gates. In this talk, we consider strong coupling between a microwave resonator and an electronspin qubit in a double quantum dot due to an inhomogeneous magnetic field generated by a nearby nanomagnet.~[1]. Considering realistic parameters, we estimate spinresonator couplings of order $\sim 1$~MHz. Further, we show that the position of the double dot relative to the nanomagnet allows us to select between purely longitudinal and transverse couplings. While the transverse coupling may be used for quantum state transfer between the spin qubit and the resonator, the longitudinal coupling could be used in a new qubit readout scheme recently introduced for superconducting qubits [2]. [1] F. Beaudoin, D. LachanceQuirion, W. A. Coish, and M. PioroLadri\`{e}re, Nanotechnology \textbf{27}, 1 (2016). [2] N. Didier, J. Bourassa, and A. Blais, Phys. Rev. Lett. \textbf{115}, 203601 (2015). [Preview Abstract] 
Thursday, March 16, 2017 4:18PM  4:30PM 
V52.00008: Coupling a single electron spin to a microwave resonator, Part II: mitigating dephasing and relaxation F\'elix Beaudoin, Dany LachanceQuirion, Alexandre Blais, William A. Coish, Michel PioroLadri\`ere Strong coupling between a single electron spin and a microwave resonator can be achieved by correlating spin and charge degrees of freedom. This correlation makes the spin susceptible to sources of orbital dephasing and relaxation, possibly leading to error in the transfer of a quantum state between a spin qubit and the lowlying Fock states ($n=0,1$) of a resonator. In this talk, we analytically evaluate this error and explain how it can be suppressed through a combination of dynamical decoupling [1] and careful optimization of device parameters [2]. This analysis gives a clear route toward the realization of coherent state transfer between a microwave resonator and a single electron spin in a GaAs double quantum dot with a fidelity above 90$\%$. Improved dynamical decoupling sequences, lownoise environments, and longerlived microwave cavity modes may lead to substantially higher fidelities in the near future. [1] F. Beaudoin, A. Blais, and W. A. Coish. arXiv:1602.05090. [2] F. Beaudoin, D. LachanceQuirion, W. A. Coish, and M. Pioro Ladri\`ere. Nanotechnology 27, 1 (2016) [Preview Abstract] 
Thursday, March 16, 2017 4:30PM  4:42PM 
V52.00009: Quantum electrodynamics with a single nuclear spin in silicon Guilherme Tosi, Fahd Mohiyaddin, Stefanie Tenberg, Arne Laucht, Vivien Schmitt, Rajib Rahman, Gerhard Klimeck, Andrea Morello The nuclear spin state of a phosphorus donor in isotopically enriched silicon28 is an excellent system to store quantum information in the solid state. The nearly noisefree magnetic environment and the spinâ€™s insensitivity to electric fields yield a solidstate qubit with record coherence times. However, these very features also render coupling to other quantum systems very challenging. Here we propose a novel method that uses electric fields to interface phosphorus nuclear spins with other quantum mechanical degrees of freedom. It consists of a Raman process where a microwave magnetic drive is supplemented by an electricallydriven timedependent modulation of the hyperfine coupling to a surrounding electron. Applications of this method include the coupling of a single nuclear spin to a microwave resonator, and the long distance coupling of two nuclear spins via electric dipoledipole interactions. Most importantly, despite being strongly coupled to other degrees of freedom via electric fields, the nuclear qubit remains highly immune to electric noise due to a new stabilization mechanism in which the magnetic drive ACStark shifts the qubit precession frequency to create a secondorder clock transition. [Preview Abstract] 
Thursday, March 16, 2017 4:42PM  4:54PM 
V52.00010: Electrically Driving Donor Spin Qubits in Silicon Using Photonic Bandgap Resonators A. J. Sigillito, A. M. Tyryshkin, S. A. Lyon In conventional experiments, donor nuclear spin qubits in silicon are driven using radiofrequency (RF) magnetic fields. However, magnetic fields are difficult to confine at the nanoscale, which poses major issues for individually addressable qubits and device scalability. Ideally one could drive spin qubits using RF electric fields, which are easy to confine, but spins do not naturally have electric dipole transitions. In this talk, we present a new method for electrically controlling nuclear spin qubits in silicon by modulating the hyperfine interaction between the nuclear spin qubit and the donorbound electron. By fabricating planar superconducting photonic bandgap resonators, we are able to use pulsed electronnuclear double resonance (ENDOR) techniques to selectively probe both electrically and magnetically driven transitions for $^{\mathrm{31}}$P and $^{\mathrm{75}}$As nuclear spin qubits. The electrically driven spin resonance mechanism allows qubits to be driven at either their transition frequency, or at onehalf their transition frequency, thus reducing bandwidth requirements for future quantum devices. Moreover, this form of control allows for higher qubit densities and lower power requirements compared to magnetically driven schemes. In our proofofprinciple experiments we demonstrate electrically driven Rabi frequencies of approximately 50 kHz for widely spaced (10 $\mu $m) gates which should be extendable to MHz for nanoscale devices. [Preview Abstract] 
Thursday, March 16, 2017 4:54PM  5:06PM 
V52.00011: Compressibility measurements using a circuit QED architecture Matthieu Desjardins, Jeremie Viennot, Matthieu Dartiailh, Laure Bruhat, Matthieu Delbecq, Minchul Lee, MahnSoo Choi, Audrey Cottet, Takis Kontos Quantum dots exhibit a wide variety of many body phenomena. A circuit QED architecture could also be instrumental for understanding them because it allows one to directly probe the compressibility of an electronic system. One of the most paradigmatic phenomenon is the Kondo effect which is at the heart of many electron correlation effects. We will show that a circuit QED architecture has allowed us to observe the decoupling of spin and charge excitations in a Kondo system. The Kondo resonance, visible in the conductance of the quantum dot, is 'transparent' to the microwave cavity photons. This reveals the freezing of charge dynamics. Our setup could be generalized to other types of mesoscopic circuits with manybody correlations and used to perform quantum simulation of fermionboson systems. [Preview Abstract] 
Thursday, March 16, 2017 5:06PM  5:18PM 
V52.00012: Squeezing microwave resonator via parametric interaction driven by a quantum dot Udson C. Mendes, Christophe Mora It has recently been demonstrated experimentally and theoretically that a DC and ACvoltage biased tunnel junction produces squeezed microwave. In this linear conductor, squeezing is generated via dissipation rather than parametric interaction. In this talk, we will first establish that a quantum dot drives parametrically the microwave resonator that it is coupled to. Then, we will show how to achieve strong squeezing by engineering the tunnel coupling between the quantum dot and the metallic leads. [Preview Abstract] 
Thursday, March 16, 2017 5:18PM  5:30PM 
V52.00013: CurrentTunable NbTiN Coplanar Photonic Bandgap Resonators A. Asfaw, A. J. Sigillito, A. M. Tyryshkin, S. A. Lyon Coplanar waveguide resonators have been used in several experimental settings, from superconducting qubits to electron spin resonance. In our particular application of electron spin resonance, these resonators provide increased sensitivity to electron spins due to the small mode volume. Experiments have shown that these resonators can be used to readout as few as 300 spins per shot. Recently, photonic bandgap resonators have been shown to extend the advantages of traditional CPW resonators by allowing spin manipulation both at microwave and radio frequencies, thereby enabling both electron and nuclear spin resonance within the same resonator. We present measurements made using photonic bandgap resonators fabricated with thin NbTiN films which demonstrate microwave tunability of the resonator by modulating the kinetic inductance of the superconductor. Driving a small direct current through the center pin of the resonator allows us to tune the resonant frequency by over 30 MHz around 6.4 GHz while maintaining a quality factor over 8000 at 4.8K. This provides fast and simple tunability of coplanar waveguide resonators and opens new possibilities for multiple frequency electron spin resonance experiments. [Preview Abstract] 
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