31 research outputs found
Strong Coupling Cavity QED with Gate-Defined Double Quantum Dots Enabled by a High Impedance Resonator
The strong coupling limit of cavity quantum electrodynamics (QED) implies the
capability of a matter-like quantum system to coherently transform an
individual excitation into a single photon within a resonant structure. This
not only enables essential processes required for quantum information
processing but also allows for fundamental studies of matter-light interaction.
In this work we demonstrate strong coupling between the charge degree of
freedom in a gate-detuned GaAs double quantum dot (DQD) and a frequency-tunable
high impedance resonator realized using an array of superconducting quantum
interference devices (SQUIDs). In the resonant regime, we resolve the vacuum
Rabi mode splitting of size MHz at a resonator linewidth
MHz and a DQD charge qubit dephasing rate of MHz extracted independently from microwave spectroscopy in the dispersive
regime. Our measurements indicate a viable path towards using circuit based
cavity QED for quantum information processing in semiconductor nano-structures
Entanglement Stabilization using Parity Detection and Real-Time Feedback in Superconducting Circuits
Fault tolerant quantum computing relies on the ability to detect and correct
errors, which in quantum error correction codes is typically achieved by
projectively measuring multi-qubit parity operators and by conditioning
operations on the observed error syndromes. Here, we experimentally demonstrate
the use of an ancillary qubit to repeatedly measure the and parity
operators of two data qubits and to thereby project their joint state into the
respective parity subspaces. By applying feedback operations conditioned on the
outcomes of individual parity measurements, we demonstrate the real-time
stabilization of a Bell state with a fidelity of in up to 12
cycles of the feedback loop. We also perform the protocol using Pauli frame
updating and, in contrast to the case of real-time stabilization, observe a
steady decrease in fidelity from cycle to cycle. The ability to stabilize
parity over multiple feedback rounds with no reduction in fidelity provides
strong evidence for the feasibility of executing stabilizer codes on timescales
much longer than the intrinsic coherence times of the constituent qubits.Comment: 12 pages, 10 figures. Update: Fig. 5 correcte
Gate-tunable kinetic inductance parametric amplifier
Superconducting parametric amplifiers play a crucial role in the preparation
and readout of quantum states at microwave frequencies, enabling high-fidelity
measurements of superconducting qubits. Most existing implementations of these
amplifiers rely on the nonlinearity from Josephson junctions, superconducting
quantum interference devices or disordered superconductors. Additionally,
frequency tunability arises typically from either flux or current biasing. In
contrast, semiconductor-based parametric amplifiers are tunable by local
electric fields, which impose a smaller thermal load on the cryogenic setup
than current and flux biasing and lead to vanishing crosstalk to other on-chip
quantum systems. In this work, we present a gate-tunable parametric amplifier
that operates without Josephson junctions, utilizing a proximitized
semiconducting nanowire. This design achieves near-quantum-limited performance,
featuring more than 20 dB gain and a 30 MHz gain-bandwidth product. The absence
of Josephson junctions allows for advantages, including substantial saturation
powers of -120dBm, magnetic field compatibility up to 500 mT and frequency
tunability over a range of 15 MHz. Our realization of a parametric amplifier
supplements efforts towards gate-controlled superconducting electronics,
further advancing the abilities for high-performing quantum measurements of
semiconductor-based and superconducting quantum devices.Comment: 12 pages, 11 figure