A low power photoemission source for electrons on liquid helium

Electrons on the surface of liquid helium are a widely studied system that may also provide a promising method to implement a quantum computer. One experimental challenge in these studies is to generate electrons on the helium surface in a reliable manner without heating the cryo-system. An electron source relying on photoemission from a zinc film has been previously described using a high power continuous light source that heated the low temperature system. This work has been reproduced more compactly by using a low power pulsed lamp that avoids any heating. About 5e3 electrons are collected on 1 cm^2 of helium surface for every pulse of light. A time-resolved experiment suggests that electrons are either emitted over or tunnel through the 1eV barrier formed by the thin superfluid helium film on the zinc surface. No evidence of trapping or bubble formation is seen.Comment: 9 pages, 3 figures, submitted to J. Low Temp. Phy

Power of Anisotropic Exchange Interactions: Universality and Efficient Codes for Quantum Computing

We study the quantum computational power of a generic class of anisotropic solid state Hamiltonians. A universal set of encoded logic operations are found which do away with difficult-to-implement single-qubit gates in a number of quantum computer proposals, e.g., quantum dots and donor atom spins with anisotropic exchange coupling, quantum Hall systems, and electrons floating on helium.We show how to make the corresponding Hamiltonians universal by encoding one qubit into two physical qubits, and by controlling nearest neighbor interactions.Comment: 5 pages, no figures. v4: Title and abstract changed. Added paragraph on state preparation and measurement. Parafermionic notation replaced with standard qubit notation. For treatment of qubits as parafermions see http://xxx.lanl.gov/abs/quant-ph/010907

Piezoacoustics for precision control of electrons floating on helium

Piezoelectric surface acoustic waves (SAWs) are powerful for investigating and controlling elementary and collective excitations in condensed matter. In semiconductor two-dimensional electron systems SAWs have been used to reveal the spatial and temporal structure of electronic states, produce quantized charge pumping, and transfer quantum information. In contrast to semiconductors, electrons trapped above the surface of superfluid helium form an ultra-high mobility, two-dimensional electron system home to strongly-interacting Coulomb liquid and solid states, which exhibit non-trivial spatial structure and temporal dynamics prime for SAW-based experiments. Here we report on the coupling of electrons on helium to an evanescent piezoelectric SAW. We demonstrate precision acoustoelectric transport of as little as ~0.01% of the electrons, opening the door to future quantized charge pumping experiments. We also show SAWs are a route to investigating the high-frequency dynamical response, and relaxational processes, of collective excitations of the electronic liquid and solid phases of electrons on helium.Comment: Main manuscript: 15 pages, 3 figures; Supplemental Information: 11 pages, 3 figures, 1 tabl

Sensitive detection of millimeter wave electric field by driving trapped surface-state electrons

Sensitive detection of electromagnetic wave electric field plays an important role for electromagnetic communication and sensing. Here, we propose a quantum sensor to sensitively detect the electric field of the millimeter (mm) wave. The quantum sensor consists of many surface-state electrons trapped individually on liquid helium by a scalable electrode-network at the bottom of the helium film. On such a chip, each of the trapped electrons can be manipulated by the biased dc-current to deliver the strong spin-orbit couplings. The mm wave signal to be detected is applied to non-dispersively drive the orbital states of the trapped electrons, just resulting in the Stark shifts of the dressed spin-orbital states. As a consequence, the electric field of the applied mm wave could be detected sensitively by using the spin-echo interferometry of the long-lived spin states of the electrons trapped on liquid helium. The reasonable accuracy of the detection and also the feasibility of the proposal are discussed.Comment: 8 page

Signal and Charge Transfer Efficiency of Few Electrons Clocked on Microscopic Superfluid Helium Channels

Electrons floating on the surface of liquid helium are possible spin-qubits for quantum information processing. Varying electric potentials are not expected to modify spin states, which allows their transport on helium using a charge-coupled device (CCD)-like array of underlying gates. This approach depends upon efficient inter-gate transfer of individual electrons. Measurements are presented here of the charge transfer efficiency (CTE) of few electrons clocked back and forth above a short microscopic CCD-like structure. A charge transfer efficiency of 0.99999992 is obtained for a clocking frequency of 800 kHz.Comment: 13 pages including 3 figure