Surface‐state electrons on liquid helium, have been proposed as condensed matter qubits. We have demonstrated that small numbers of electrons, including a single isolated electron, can be held in an electrostatic trap above the surface of superfluid helium and individually detected using a superconducting single‐electron transistor (SET). A new design for a quantum information processor, using an array of electron traps on liquid helium, has been fabricated on a Si wafer using a superconducting A1 SET.
Surface‐state electrons on liquid helium, have been proposed as condensed matter qubits. We have demonstrated that small numbers of electrons, including a single isolated electron, can be held in an electrostatic trap above the surface of superfluid helium and individually detected using a superconducting single‐electron transistor (SET). A new design for a quantum information processor, using an array of electron traps on liquid helium, has been fabricated on a Si wafer using a superconducting A1 SET.
We show that small numbers of electrons, including a single isolated electron, can be held in an electrostatic trap above the surface of superfluid helium. A potential well is created using microfabricated electrodes in a 5 μm diameter pool of helium. Electrons are injected into the trap from an electron reservoir on a helium microchannel. They are individually detected using a superconducting single-electron transistor as an electrometer. A Coulomb staircase is observed as electrons leave the trap one–by–one until the trap is empty. A design for a scalable quantum information processor using an array of electron traps is presented.
It has been proposed in literature that a quantum computer can be made utilizing the electronic states of electrons bound to the surface of liquid helium. One can model a single electron on the surface as a 1d hydrogenic atom, providing a set of quantum electronic states which are easily tunable, with an untuned energy gap of 0.488\\,meV (̃120 GHz) between the ground state and the first excited state, and it is these two energy levels that are proposed as the 0 and 1 state of a qubit. To that end, three microfabricated devices are needed: a low temperature electron source of low energy electrons, a detector capable of detecting single electrons, and a microstructure capable of trapping and Stark shifting the energy levels of individual electrons in proximity close enough to perform multiple qubit operations. This dissertation contains a description of the devices microfabricated for these purposes. An electron source based on porous silicon was fabricated, tested, and proven to provide low energy electrons. Other more conventional techniques based on a thoriated tungsten filament were also explored. For electron detection, we have fabricated a transition edge superconducting microbolometer. Tests have shown it is capable of detecting a few eV of energy. For the microstructure, we fabricated a series of columns 200 nm in diameter, 1.5[mu]m in height, separated by 500 nm. For later tests, a microelectrode exposed through a 10[mu]m diameter hole in a ground plane was used. Initial experiments describing bolometer designs and electron confinement are discussed, as well as proposed microfabrication redesign to continue this work. Numerical time series computations of both single (NOT, PHASE) and two qubit (SWAP, [square root]SWAP, CNOT) gates are also presented
Electrons trapped on the surface of cryogenic substrates (liquid helium, solid neon, or hydrogen) are an emerging platform for quantum information processing made attractive by the inherent purity of the electron environment, the scalability of trapping devices, and the predicted long lifetime of electron spin states. Here we demonstrate the spatial control and detection of single electrons above the surface of liquid helium at temperatures above 1 K. A superconducting coplanar waveguide resonator is used to read out the charge state of an electron trap defined by gate electrodes beneath the helium surface. Dispersive frequency shifts are observed as the trap is loaded with electrons, from several tens down to single electrons. These frequency shifts are in good agreement with our theoretical model that treats each electron as a classical oscillator coupled to the cavity field. This sensitive charge readout scheme can aid efforts to develop large-scale quantum processors that require the high cooling powers available in cryostats operating above 1 K.
Electrons on helium form a unique two-dimensional system on the interface of liquid helium and vacuum. A small number of trapped electrons on helium exhibits strong interactions in the absence of disorder, and can be used as a qubit. Trapped electrons typically have orbital frequencies in the microwave regime and can therefore be integrated with circuit quantum electrodynamics (cQED), which studies light-matter interactions using microwave photons. Here, we experimentally realize a cQED platform with the orbitals of single electrons on helium. We deterministically trap one to four electrons in a dot integrated with a microwave resonator, allowing us to study the electrons' response to microwaves. Furthermore, we find a single-electron-photon coupling strength of [Formula: see text] MHz, greatly exceeding the resonator linewidth [Formula: see text] MHz. These results pave the way towards microwave studies of Wigner molecules and coherent control of the orbital and spin state of a single electron on helium.
Abstract Surface-state electrons floating on liquid Helium have been served as one of the great potential experimental platforms to implement quantum computation, wherein the qubits are usually encoded by either the lowest two levels of the vertical vibrations (i.e., Hydrogen-like atoms) or the electronic spins. Given the relevant operations require additional techniques, such as the corresponding millimeter-wave or magnetic field manipulations, here we investigate how to implement the scalable quantum computation with a trapped electron array by alternatively using the usual centimeter-wave manipulating techniques. This is because the eigenfrequency of the present qubit, encoded by the two lowest levels of the lateral vibration of the trapped electron, is limited in the centimeter-wave band. We show that, by biasing the electrodes properly and driving the coplanar waveguide transmission line resonator, the electrons can be individually trapped in a series of anharmonic potentials on liquid Helium. Therefore, the well-developed circuit quantum electrodynamics technique for the implementation of superconducting quantum computation can be conveniently utilized here in the present quantum computing platform (proposed firstly in Phys Rev Lett 105:040503, 2010, to implement the fundamental logic gates, typically such as the single-qubit rotations of the individually addressable trapped electrons, the switchable two-qubit manipulations between the electrons trapped in the distant traps, and also the high-fidelity readouts of the target qubits. The feasibility of the proposal is also discussed by numerical simulations.
Electrons trapped on the surface of superfluid helium have been thought of as a useful resource for quantum computing. Such electrons show long coherence of their surface-bound (Rydberg) states combined with their easy electrostatic manipulation. Recent proposals have explored the possibility of coupling the spin state of an electron and the state of its quantized motion, with the promise of a highly scalable two-dimensional architecture for a quantum computer. However, despite recent progress in the detection of quantized lateral motion of electrons using a circuit-QED setup, manipulation of a small number of electrons and their quantum state detection remains a challenging problem. Here, we report on the detection of the Rydberg transition of electrons on superfluid helium in an on-chip microchannel device in which electrons are moved and trapped by a set of electrostatic gates. A highly sensitive image-charge detection system allows us to not only resolve the transition spectra of such electrons, but also perform the device characterization. The demonstrated sensitivity shows the feasibility of detecting the Rydberg transition of a single electron, which can open an alternate pathway for a nondestructive spin-state readout.