Scaling of Majorana Zero-Bias Conductance Peaks Nichele, Fabrizio; Drachmann, Asbjørn C C; Whiticar, Alexander M ...
Physical review letters,
09/2017, Volume:
119, Issue:
13
Journal Article
Peer reviewed
Open access
We report an experimental study of the scaling of zero-bias conductance peaks compatible with Majorana zero modes as a function of magnetic field, tunnel coupling, and temperature in one-dimensional ...structures fabricated from an epitaxial semiconductor-superconductor heterostructure. Results are consistent with theory, including a peak conductance that is proportional to tunnel coupling, saturates at 2e^{2}/h, decreases as expected with field-dependent gap, and collapses onto a simple scaling function in the dimensionless ratio of temperature and tunnel coupling.
Quantum information science has the potential to revolutionize modern technology by providing resource-efficient approaches to computing
, communication
and sensing
. Although the physical qubits in ...a realistic quantum device will inevitably suffer errors, quantum error correction creates a path to fault-tolerant quantum information processing
. Quantum error correction, however, requires that individual qubits can interact with many other qubits in the processor. Engineering such high connectivity can pose a challenge for platforms such as electron spin qubits
, which naturally favour linear arrays. Here we present an experimental demonstration of the transmission of electron spin states via the Heisenberg exchange interaction in an array of spin qubits. Heisenberg exchange coupling-a direct manifestation of the Pauli exclusion principle, which prevents any two electrons with the same spin state from occupying the same orbital-tends to swap the spin states of neighbouring electrons. By precisely controlling the wavefunction overlap between electrons in a semiconductor quadruple quantum dot array, we generate a series of coherent SWAP operations to transfer both single-spin and entangled states back and forth in the array without moving any electrons. Because the process is scalable to large numbers of qubits, state transfer through Heisenberg exchange will be useful for multi-qubit gates and error correction in spin-based quantum computers.
Using a singlet-triplet spin qubit as a sensitive spectrometer of the GaAs nuclear spin bath, we demonstrate that the spectrum of Overhauser noise agrees with a classical spin diffusion model over 6 ...orders of magnitude in frequency, from 1 mHz to 1 kHz, is flat below 10 mHz, and falls as 1/f^{2} for frequency f≳1 Hz. Increasing the applied magnetic field from 0.1 to 0.75 T suppresses electron-mediated spin diffusion, which decreases the spectral content in the 1/f^{2} region and lowers the saturation frequency, each by an order of magnitude, consistent with a numerical model. Spectral content at megahertz frequencies is accessed using dynamical decoupling, which shows a crossover from the few-pulse regime (≲16π pulses), where transverse Overhauser fluctuations dominate dephasing, to the many-pulse regime (≳32 π pulses), where longitudinal Overhauser fluctuations with a 1/f spectrum dominate.
PDF
