Bulletin of the American Physical Society
APS March Meeting 2023
Volume 68, Number 3
Las Vegas, Nevada (March 5-10)
Virtual (March 20-22); Time Zone: Pacific Time
Session Q67: Hybrid Quantum Systems IIIFocus
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Sponsoring Units: DQI Chair: Yogesh Patil, Yale University Room: Room 412 |
Wednesday, March 8, 2023 3:00PM - 3:12PM |
Q67.00001: Electron charge qubits on solid neon with 0.1 millisecond coherence time Xinhao Li, Xianjing Zhou, Qianfan Chen, Gerwin Koolstra, Ge Yang, Brennan Dizdar, Xu Han, Xuefeng Zhang, David Schuster, Dafei Jin Electron charge qubits built upon traditional semiconductors and superconductors are historically known to suffer from a short coherence time that hardly exceeds 10 microseconds. The primary source of decoherence comes from the inevitable charge noise in conventional host materials. However, electron charge qubits possess unparalleled advantages in their simplicities in design, fabrication, control, and readout. Here, we report our experimental realization of ultralong-coherence electron charge qubits based on a unique platform that we recently developed. The qubits utilize the motional states of isolated single electrons trapped on an ultraclean solid neon surface in vacuum and strongly coupled with microwave photons in an on-chip superconducting resonator. The measured relaxation time T1 and coherence time T2 are both on the order of 0.1 milliseconds. A single-shot readout fidelity of 97.5% without using a quantum-limited amplifier and a single-qubit gate fidelity of 99.95% using the Clifford-based randomized benchmarking are obtained. Simultaneous strong coupling of two qubits with the same resonator is demonstrated, as a first step toward two-qubit entangling gates for universal quantum computing. These results manifest that the electron-on-solid-neon (eNe) charge qubits have outperformed all the existing charge qubits to date and rivaled the state-of-the-art superconducting transmon qubits. The eNe qubit platform holds promise to become an ideal qubit platform and provides new insights toward scalable quantum computing architectures. |
Wednesday, March 8, 2023 3:12PM - 3:24PM |
Q67.00002: Confining Electrons Floating on Helium in Sub-Micron Quantum Dot Arrays Mayer M Feldman, Kyle E Castoria, Stephen A Lyon The semiconductor quantum dot community’s recent success in performing high fidelity single- and two-qubit[1] logical operations has brought the electron spin state to the forefront of quantum information. The decoherence free nature of an electron floating on helium makes it an attractive solution to mitigating decoherence limitations inherent to host semiconductors crystals such as low-lying valley states and nuclear spin-spin interactions. However, the first step in realizing a spin qubit is reliably confining and controlling the charge degree of freedom of a single electron. Previous demonstrations in confinement have been successful in adding electrons and detecting single transitions in quantum dots on the order of 1-5 μm[2], over an order of magnitude larger than a single electron wavefunction. The large dots make it difficult to spatially pinpoint and precisely manipulate charges both of which are requirements for high fidelity qubit operation. With this in mind, we fabricate multiple arrays containing millions of highly uniform, sub-micron quantum dots and explore the effect that dot size has on the electron confinement. |
Wednesday, March 8, 2023 3:24PM - 3:36PM |
Q67.00003: Towards a mechanical qubit in a carbon nanotube Roger Tormo Queralt, Adrian Bachtold, Christoffer B Moller, Andrew N Cleland, David Czaplewski, Fabio Pistolesi, chandan Samantha, Sergio Lucio de Bonis, Sergio Lucio de Bonis, Sergio Lucio de Bonis Mechanical resonators based on carbon nanotubes are an exceptional platform to study the coupling between mechanical motion[1] and electron transport[2]. Recently, it has been shown that the second flexural mode of a carbon nanotube mechanical resonator may be coupled to a double quantum dot interdot transition[3]. In the ultra-strong coupling limit, the electron transition induces enough anharmonicity in the energy dispersion curve of the harmonic oscillator that the system can be used as a qubit[4]. |
Wednesday, March 8, 2023 3:36PM - 3:48PM |
Q67.00004: Correlated transport of electrons on helium through a gate-defined island Niyaz Beysengulov, Camille A Mikolas, Austin J Schleusner, Joe M Kitzman, David G Rees, Johannes Pollanen Field-effect control of low-dimensional electron systems in nanoscale devices has enabled the exploration of a wide variety of mesoscopic quantum phenomena in semiconductors such as the quantized electrical conductance produced by Coulomb blockade effects. In contrast to semiconductor systems, electrons trapped at the boundary of a liquid helium-vacuum interface realize a non-degenerate two-dimensional electron system with ultra-high mobility and unique mesoscopic transport behavior when subjected to microchannel confinement. Here we report on the transport behavior of strongly-interacting liquid and solid states of electrons on helium through a controllable electron-island gate. Our results reveal the effect of Coulomb interaction-induced correlations in each phase as the electrons are transported through the island/constriction. |
Wednesday, March 8, 2023 3:48PM - 4:00PM |
Q67.00005: Collective excitations of microchannel-confined electrons on helium Camille A Mikolas, Niyaz Beysengulov, Austin J Schleusner, Joe M Kitzman, David G Rees, Johannes Pollanen Electrons floating above the surface of superfluid helium (eHe) are a unique platform to investigate the high-frequency collective dynamics of ultra-high mobility trapped electron systems. Here we present the results of recent experiments in which the electron system is simultaneously subjected to microchannel confinement and GHz-frequency microwave excitation. The microchannel device provides precision control of the electron density and enables access to both quasi-one-dimensional electron chains as well as two-dimensional electron sheets. In this device, we observe density-dependent resonant-like features in the electron transport data, which originate from collective excitations of the electron system in the microchannel. Additionally, we present progress on developing hybrid devices composed of microchannel eHe systems coupled to superconducting coplanar waveguide resonators, which can aid in the development of future quantum information science technologies based on trapped electrons. |
Wednesday, March 8, 2023 4:00PM - 4:12PM |
Q67.00006: High-frequency transport of microchannel-confined electrons on helium Austin J Schleusner, Niyaz Beysengulov, Camille A Mikolas, Joe M Kitzman, David G Rees, Johannes Pollanen Transport studies of the two-dimensional electron system trapped at the surface of liquid helium are typically carried out at relatively low driving field frequencies, where the electron system can be represented by simple lumped circuit elements. Here we present a study of the electron transport in a hybrid microchannel device under high-frequency f = 1-20 MHz driving fields. In this device the electron system on the helium surface is capacitively coupled to source and drain electron reservoir electrodes and transported through a narrow microchannel connecting the reservoirs. The analysis of the data is carried out in the framework of transmission line theory and reveals resonant behavior of the electron fluid associated with its wave-like transport nature. We discuss the possibility of these phenomena potentially arising from the inertial response of the electron system. |
Wednesday, March 8, 2023 4:12PM - 4:24PM |
Q67.00007: Development of the Electrohydrodynamic Instability of Charged Liquid Helium Surface Pranaya Kishore K Rath, Paul Leiderer, Ambarish Ghosh The surface electron density on the surface of bulk liquid helium is limited by the classical electrohydrodynamic (EHD) instability. Due to the EHD instability, the surface electrons enter the liquid helium and form Multielectron Bubbles (MEBs). This instability is not an instantaneous process; in fact, it extends over a period of time. A detailed analysis of the dynamics of the instability and its dependency on factors like charge density and electric field can be crucial in effectively manipulating the instability to obtain a stable high-density state. Though there are a few previous experimental studies on the onset of EHD instability on charged liquid helium-4 surface, the temporal dynamics of the EHD instability has not been studied yet. In this work, we present the experimental investigation of the temporal dynamics of the instability as a function of charge density and electric field. The unstable wave vectors are determined using image analysis of the acquired images and found to be matched with the theoretically expected values. The growth rate of unstable wave vectors is studied in detail and found to be limited by the kinematic viscosity of the medium. |
Wednesday, March 8, 2023 4:24PM - 4:36PM |
Q67.00008: Kelvin Probe Measurement of High Desnity, Mobile Electrons on a Thin Helium Film Supported by a Metal Substrate Kyle E Castoria, Stephen A Lyon Transport of electrons over thin helium films covering a metal substrate has proven difficult due in part to the metal’s rough surface profile and potential barriers due to discrete grain boundaries. Additionally, surface state electrons on a thin film are prevented from crossing between neighboring metal gates due to the potential barrier arising from the lack of a metal image charge directly below the electron when in the gap. Using an ultra-smooth amorphous metal with a thin central channel connecting two large area gates, we observe evidence of mobile surface state electrons at high electron density. By changing the potential of these gates, we measure density changes corresponding to electron transfer from one plate to the other. Because the gates are connected by a single channel, the electrons never cross gaps in the metal surface and because the metal alloy used (Nb16Si84) is highly resistive at cryogenic temperatures, the helium film is not significantly heated while a potential difference is applied to the connected gates. The electrons on either side of the channel are measured with a Kelvin probe technique, which can selectively measure the density of electrons on each plate. |
Wednesday, March 8, 2023 4:36PM - 4:48PM |
Q67.00009: Electron transport on thin helium film across mm long transport line Tiffany R Liu, Kyle E Castoria, Stephen A Lyon Using the spins of surface state electrons on liquid helium as qubits is a promising quantum computing platform which leverages the clean vacuum-helium interface to achieve high coherence times. Qubit initialization for such a system will require the movement of electrons from bulk to thin films of helium, which provides accelerated thermalization due to Johnson noise currents. Here, we demonstrate the efficient transport of high densities of electrons across a ~50 nm thick van der Waals helium film. Electrons are transferred between two regions of bulk helium consisting of 600 nm tall, 10 um wide channels patterned above three electrodes, allowing for the use of the Sommer-Tanner method to determine electron density. Connecting these two regions is a 5.6 um wide, 4 mm long transport line fabricated with resistive (.0056 ohm-cm at 1.8 K), amorphous NbSi which allows for reduced variations in work function and an ultrasmooth surface. When a voltage is applied along this thin, resistive gate we establish a constant electric field on the electrons. Furthermore, by pulsing underlying gates positive and negative at each end of the transport region, the movement of electrons in and out of the thin film region can be timed to determine a time-of-flight electron mobility. |
Wednesday, March 8, 2023 4:48PM - 5:24PM |
Q67.00010: Characterization of magnetically levitated drops of liquid 3He and 4He Invited Speaker: Jack G Harris Liquid helium drops offer a combination of low temperature, isolation, superfluidity, and experimental access that is unique among condensed matter systems. These features can play an important role in a range of disciplines, including precision molecular spectroscopy, studies of cold chemical reactions, and fluid dynamics in classical and quantum regimes. In addition, such drops may be well-suited as nonlinear optical devices and for studies of macroscopic quantum phenomena. |
Wednesday, March 8, 2023 5:24PM - 5:36PM |
Q67.00011: Electron spin coherence on a solid neon surface Qianfan Chen, Ivar Martin, Liang Jiang, Dafei Jin A single electron floating on the surface of a condensed noble-gas liquid or solid can act as a spin qubit with ultralong coherence time, thanks to the extraordinary purity of such systems. Previous studies suggest that the electron spin coherence time on a superfluid helium (He) surface can exceed 100 s. In this paper, we present theoretical studies of the electron spin coherence on a solid neon (Ne) surface, motivated by our recent experimental realization of single-electron charge qubit on solid Ne. The major spin decoherence mechanisms investigated include the fluctuating Ne diamagnetic susceptibility due to thermal phonons, the fluctuating thermal current in normal metal electrodes, and the quasi-statically fluctuating nuclear spins of the 21Ne ensemble. We find that at a typical experimental temperature about 10 mK in a fully superconducting device, the electron spin decoherence is dominated by the third mechanism via electron–nuclear spin–spin interaction. For natural Ne with 2700 ppm abundance of 21Ne, the estimated inhomogeneous |
Wednesday, March 8, 2023 5:36PM - 5:48PM |
Q67.00012: Towards Strong Coupling in Single Electron-on-Helium Systems Brennan Dizdar, Christopher S Wang, Gerwin Koolstra, David Schuster Single electrons trapped on the surface of superfluid helium (EonHe) are a unique and versatile platform for hybrid quantum information science. An attractive approach for single electron manipulation and readout is to leverage cavity QED techniques by coupling a superconducting resonator to an electron’s translational motion, and eventually, the spin [1]. Recent work has achieved coupling between a superconducting resonator and a single electron’s translational motion [2], limited primarily by dephasing mechanisms due to helium surface vibrations. In this work, we make strides towards strong coupling by making use of high impedance TiN thin film resonators in tandem with a geometry that significantly reduces the contribution of helium surface vibrations to the single electron linewidth. We present our latest experiments in the platform towards strongly coupling the translational state of a single electron to a superconducting resonator. |
Wednesday, March 8, 2023 5:48PM - 6:00PM Author not Attending |
Q67.00013: Non-inertial motion dependent Bell state Julius Arthur A Bittermann, Marcus Huber, Matthias Fink, Rupert Ursin We investigate how non-inertial motion affects polarization entangled photonic Bell states. For this purpose, we combine a SPDC source with a rotating Sagnac interferometer. We then bring the photon pair in a superposition of co- and counter-rotation. The phase of this |Φ>-state corresponds to the Sagnac phase and is linearly dependent on the angular velocity. We can switch between a |Φ+>–state and a |Φ->–state by changing the angular velocity. Thus, our setup enables a unitary transformation by means of rotation and a Bell state manipulation via non-inertial motion. |
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