Bulletin of the American Physical Society
APS March Meeting 2019
Volume 64, Number 2
Monday–Friday, March 4–8, 2019; Boston, Massachusetts
Session S29: Semiconducting Spin Qubits, Photonic and Phononic CouplingFocus
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Sponsoring Units: DQI Chair: Xiangyu Ma, University of Delaware Room: BCEC 162A |
Thursday, March 7, 2019 11:15AM - 11:27AM |
S29.00001: Coupling superconducting qubits to traveling surface acoustic wave phonons Etienne Dumur, Kevin Satzinger, Youpeng Zhong, Hung-Shen Chang, Gregory A Peairs, Ming-Han Chou, Audrey Bienfait, Christopher Conner, Joel Grebel, Rhys G Povey, Andrew N Cleland Surface acoustic wave (SAW) devices are heavily used in classical signal processing applications. SAWs have also been proposed as a method to coherently couple disparate solid-state quantum systems, such as superconducting and semiconducting qubits[1-4]. Recently the quantum control of phonons in a SAW resonator has also been demonstrated[5]. In this talk, we report the experimental development of a device coupling two superconducting qubits through SAW phonons. The transduction of the energy quantum is performed by a unidirectional SAW transducer. We examine the influence of the material properties, coupling strategy, acoustic velocity and design on the performance of the state transfer. |
Thursday, March 7, 2019 11:27AM - 11:39AM |
S29.00002: Quantum State Transfer Using Surface Acoustic Wave Phonons Audrey Bienfait, Kevin Satzinger, Youpeng Zhong, Hung-Shen Chang, Ming-Han Chou, Christopher Conner, Etienne Dumur, Joel Grebel, Gregory A Peairs, Rhys G Povey, Andrew N Cleland Heavily used in classical signal processing, surface acoustic waves (SAWs) have also been proposed as a means to couple distant solid-state quantum systems. Several groups have reported the coherent coupling of standing SAWs modes to superconducting qubits, opening the door to the control and detection of quantum phonon states. Here, we explore the coherent coupling of superconducting qubits to propagating SAWs. The experimental device comprises a 2-mm-long SAW resonator coupled to two xmon-style qubits. The resonator operates at 4 GHz and sustains 70 standing SAW modes with a free spectral range of 2 MHz. We demonstrate that each qubit reaches the strong multi-mode regime, where the coupling to one standing mode exceeds the resonator free spectral range. We show that in this regime, each qubit can launch a propagating SAW into the resonator and capture it at a later time, showing that the SAW resonator can act as an acoustic communication channel. We perform quantum state transfer as well as remote entanglement generation between the two qubits using this acoustic channel. |
Thursday, March 7, 2019 11:39AM - 11:51AM |
S29.00003: Giant Atom Bounded in Continuum Shangjie Guo, Yidan Wang, Thomas Purdy, Jacob Taylor Tremendous progress in coupling light to matter has enabled strong coupling of qubits to modes of a photonic or phononic resonator. Here we consider what happens in the phononic case when the qubit is coupled to an electromagnetic antenna that enables supersonic propagation of the qubit oscillations. One can consider this as a giant – many wavelength-long – atom from the perspective of the phonons. We find that even in the absence of phononic resonances, as the atom size is increased, new bound states emerge from the continuum. We find a toy model that captures these effects while being exactly solvable. Compared to a sub-wavelength size atom, the bound states of this non-Markovian giant atom has localized wavefunctions, reduced dissipation, and amplified vacuum Rabi frequencies. This result also agrees with our generalized Levinson’s theorem, as the number of bound states always equals the winding number of transmission phase. Application of this approach to surface acoustic wave devices will be considered. |
Thursday, March 7, 2019 11:51AM - 12:27PM |
S29.00004: Solid-state quantum interfaces of spins and photons Invited Speaker: Mete Atature Optically active spins in solids offer exciting opportunities as scalable and feasible quantum-optical devices. Numerous material platforms, such as diamond, silicon carbide and semiconductors, are under investigation, where each platform brings advantages along with challenges. For example, diamond nitrogen-vacancy centre is a fantastic host for spins, yet suffers from its optical properties. In contrast, the brightness and the coherence of photons from semiconductor quantum dots remain practically unchallenged today, while the electronic spin coherence is modest owing to the magnetic noise generated by the nuclear spins of the quantum dot. In this talk, I will present an overview of the current progress to overcome such challenges for solid-state spin-photon interfaces in two example platforms: First, I will highlight the diamond group-IV vacancy centres and their promise to combine desirable optical and spin properties. Then, I will finish with the semiconductor quantum dots and their potential to transform their nuclei from nuisance to resource. |
Thursday, March 7, 2019 12:27PM - 12:39PM |
S29.00005: Tunable coupling of a double quantum dot spin system to a mechanical resonator Samuel Carter, Allan S Bracker, Michael K Yakes, Maxim Zalalutdinov, Mijin Kim, Chul Soo Kim, Bumsu Lee, Daniel G Gammon Hybrid systems in which a mechanical resonator is coupled to a microscopic quantum system are of strong practical and fundamental interest. Achieving a large interaction strength is vital for many goals in this field, and the ability to tune this coupling is also valuable. This has been challenging in solid state spin systems, where often the coupling is weak and fixed. Here we use pairs of coupled InAs quantum dots embedded within GaAs cantilevers to achieve high spin-mechanical coupling through strain. One electron is injected into each dot, with the tunnel coupling inducing a splitting between the singlet and triplet spin states. While optically driving motion of the cantilever, we measure the time-dependent shifts of the singlet and triplet transitions and find that the spin splitting can be highly sensitive to the motion-induced strain. This sensitivity depends strongly on the electrical bias of the system and can even be tuned to zero. The results can be explained by the difference in strain experienced by the two QDs, due to their different positions in the cantilever, which results in a change in the exchange interaction. |
Thursday, March 7, 2019 12:39PM - 12:51PM |
S29.00006: Coupling a mechanical oscillator to a parametric amplifier David Zoepfl, Mathieu L. Juan, Christian Schneider, Gerhard Kirchmair In our experiment, we inductively couple a mechanical oscillator to a microwave circuit. We place a magnet on the tip of the mechanical resonator, a cantilever, which leads to a position dependent magnetic field. This field is coupled via a SQUID embedded into a microwave resonator: its resonance frequency depends on flux and consequently on the position of the cantilever. In addition to being a flux sensitive element, the SQUID also constitutes a non-linear element. This non-linear system is modelled with the Duffing model, describing our measurement data with good accuracy. The non-linearity also enables us to use the resonator as a parametric amplifier, and boost the system’s sensitivity. |
Thursday, March 7, 2019 12:51PM - 1:03PM |
S29.00007: Hardware-efficient quantum random access memory using hybrid quantum acoustic systems Connor Hann, Chang-Ling Zou, Yaxing Zhang, Yiwen Chu, Robert Schoelkopf, Steven Girvin, Liang Jiang Hybrid quantum systems where acoustic resonators couple to superconducting qubits are promising quantum information platforms. High quality factors and small mode volumes make acoustic modes ideal quantum memories, while the qubit coupling enables the initialization and manipulation of quantum states. In this talk we consider the practical applications of multi-mode quantum acoustic systems as hardware-efficient quantum processors. Quantum gates between different acoustic modes can be implemented using resonant interactions between the phonons and qubit, but such gates are vulnerable to qubit decoherence. As an alternative, we propose the use of off-resonant interactions that only virtually excite the qubit. This virtual approach overcomes limitations placed by qubit decoherence and attains considerably higher fidelities for long-lived acoustic modes. Given advances in performance, we propose a quantum acoustic implementation of a quantum random access memory (qRAM). We show how information can be routed through the system such that data stored in memory modes can be accessed in superposition according to the state of designated address modes—implementing a qRAM on a single chip. |
Thursday, March 7, 2019 1:03PM - 1:15PM |
S29.00008: Toward the preparation of sub-Poissonian states in a low frequency mechanical oscillator Xizheng Ma, Jeremie Viennot, Shlomi Kotler, Konrad Lehnert Preparation of non-classical states of motion in a macroscopic object has been an ambition in the field of opto- and eletro-mechanics. We propose a protocol for the preparation of one type of non-classical state, the sub-Poissonian state. We dispersively couple a Cooper-pair box qubit to a 25 MHz aluminum drumhead mechanical oscillator, and enter the phonon number sensitive regime [1]. In this regime, the motion-induced AC Stark shift on the qubit allows us to address phonon populations with a number resolution of 7, and to extract the phonon distribution via the qubit lineshape. Using sideband transitions between the qubit and mechanics, we demonstrate progress towards preparing the mechanical oscillator in a sub-Poissonian state, where the variance in the phonon distribution is less than the mean phonon number. |
Thursday, March 7, 2019 1:15PM - 1:27PM |
S29.00009: Resolving Phonon Number States with an Acoustic Ramsey Interferometer Lucas Sletten, Bradley Moores, K. W. Lehnert The rise of quantum control over surface acoustic waves (SAWs) introduced a novel concept: a “giant atom” many wavelengths long. The large size of the atom, formed by a transmon qubit with a piezoelectric transducer, generates fine frequency features in the qubit-phonon interaction strength that are determined by the shape of the transducer. Here, we combine a multi-mode SAW cavity with a qubit whose transducer is spatially engineered to enter the strong dispersive regime. The transducer comprises two halves separated by 38 wavelengths that, in close analogy to Ramsey interferometry, generate narrow frequency fringes in the qubit-phonon coupling. We observe these fringes both as a sharp frequency dependence in the qubit emission of unconfined phonons and as a modulated coupling strength to acoustic cavity modes. This modulation creates frequency regions of strong coupling in close proximity to windows of vanishing coupling, a combination that enables both dispersive operation and a coupling strength that is comparable to the free spectral range. The strong coupling creates a large dispersive shift that exceeds both qubit and acoustic linewidths. |
Thursday, March 7, 2019 1:27PM - 1:39PM |
S29.00010: Nonexponential decay of a giant artificial atom Gustav Andersson, Baladitya Suri, Lingzhen Guo, Thomas Aref, Per Delsing The interaction between light and atoms has been conventionally studied using small atoms interacting with electromagnetic radiation of wavelengths that are several orders of magnitude larger than the atomic dimensions. In contrast, quantum acoustic experiments allow reaching the giant atom regime, where the coupled field wavelength is orders of magnitude smaller than the atomic dimensions. This is achieved by coupling a superconducting qubit to surface acoustic waves on a piezoelectric substrate at two points with separation on the order of 100 wavelengths. This approach is comparable to controlling the radiation of the atom by attaching an antenna. The slow velocity of sound leads to a significant internal time-delay for the field to propagate across the giant atom, and thus strongly non-Markovian dynamics. We demonstrate signatures of this non-Markovianity in the frequency spectrum as well as time domain relaxation of the giant atom. |
Thursday, March 7, 2019 1:39PM - 1:51PM |
S29.00011: Strong coupling of a transmon qubit and a phononic crystal cavity array Patricio Arrangoiz-Arriola, Alex Edward Wollack, Marek Pechal, Zhaoyou Wang, Wentao Jiang, Timothy McKenna, Amir Safavi-Naeini Coupling superconducting circuits to nanomechanical systems opens up new opportunities in quantum acoustics (e.g. QND phonon detection) and the exploration of technologically-relevant devices such as quantum memory elements. In particular, phononic crystal cavities (PCCs), which localize sound at the wavelength scale, show great promise as ultra-compact, long-lived mechanical elements which can be strongly coupled to a superconducting circuit despite being orders of magnitude smaller. Building upon our previous work, we now demonstrate coupling of a transmon qubit to an array of PCCs with mode frequencies in the 2.0-2.4 GHz range. We fabricate the qubit and associated control and readout circuitry on a silicon substrate and the PCCs on a suspended thin film of lithium niobate, effectively forming an array of one-dimensional “phononic wires” with localized resonances at a set of precisely engineered frequencies. The phononic defects sites are coupled to the qubit via superconducting electrodes patterned directly on top of the cavity mirrors. We measure qubit-phonon coupling rates in excess of 10 MHz, putting the system well in the strong coupling regime. |
Thursday, March 7, 2019 1:51PM - 2:03PM |
S29.00012: Single-photon emission driven by a surface acoustic wave in a lateral undoped GaAs/AlGaAs n-i-p junction, resolved in time, position and energy Antonio Rubino, Tzu-Kan Hsiao, Yousun Chung, Seok-Kyun Son, Hangtian Hou, Jorge Pedros, Ateeq Nasir, Gabriel Ethier-Majcher, Megan J Stanley, Richard Thomas Phillips, Thomas A Mitchell, Jonathan Griffiths, Ian Farrer, David A Ritchie, Christopher J Ford We induce both electrons and holes in an undoped GaAs quantum well using surface gates to form a lateral n-i-p junction, which is confined into a quasi-1D channel by etching and side gates. A surface acoustic wave (SAW) collects electrons in the n-region and transports them into the p-region where they recombine with holes. The narrow channel and the SAW potential can combine to limit the number of electrons pumped per cycle to 1, so the recombination with holes should produce a stream of single photons. We observe SAW-driven light emission. Time-resolved electroluminescence in the regime where less than one electron is transported per cycle on average shows a recombination time of 100 ps. The second-order correlation, g2(0), measured using a Hanbury Brown and Twiss interferometer with single-photon detectors, shows the signature of antibunching and satisfies the criterion for being a single-photon source, g2(0)<0.5. SAW-driven pumping holes into a region of electrons shows a much shorter recombination time. The dynamics is investigated in detail by resolving simultaneously the emission time, position in the channel, and energy, at T=1.5K. |
Thursday, March 7, 2019 2:03PM - 2:15PM |
S29.00013: Demonstration of the Generalized Kennedy Receiver as a Near Quantum-Optimal Measurement for the Discrimination of Weak Classical Optical States Jonathan Habif, Arunkumar Jagannathan We describe an experimental testbed demonstrating quantum measurements on a single spatio-temporal, polarization mode, photon-starved classical state of light. The measurements are designed to optimally discriminate between coherent and incoherent optical states at mean photon numbers n < 2. A narrow-linewidth, 780 nm laser is used to prepare a coherent state or a thermal state in a single spatio-temporal, polarization mode. Three measurement strategies are implemented for the discrimination problem: photon counting, shot-noise limited coherent detection, and the near-optimal, generalized Kennedy receiver. For each receiver type we present discrimination error probability measurements as a function of the mean photon number of the received optical state. |
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