12 research outputs found
Broadband parametric amplification for multiplexed SiMOS quantum dot signals
Spins in semiconductor quantum dots hold great promise as building blocks of
quantum processors. Trapping them in SiMOS transistor-like devices eases future
industrial scale fabrication. Among the potentially scalable readout solutions,
gate-based dispersive radiofrequency reflectometry only requires the already
existing transistor gates to readout a quantum dot state, relieving the need
for additional elements. In this effort towards scalability, traveling-wave
superconducting parametric amplifiers significantly enhance the readout
signal-to-noise ratio (SNR) by reducing the noise below typical cryogenic
low-noise amplifiers, while offering a broad amplification band, essential to
multiplex the readout of multiple resonators. In this work, we demonstrate a
3GHz gate-based reflectometry readout of electron charge states trapped in
quantum dots formed in SiMOS multi-gate devices, with SNR enhanced thanks to a
Josephson traveling-wave parametric amplifier (JTWPA). The broad, tunable 2GHz
amplification bandwidth combined with more than 10dB ON/OFF SNR improvement of
the JTWPA enables frequency and time division multiplexed readout of interdot
transitions, and noise performance near the quantum limit. In addition, owing
to a design without superconducting loops and with a metallic ground plane, the
JTWPA is flux insensitive and shows stable performances up to a magnetic field
of 1.2T at the quantum dot device, compatible with standard SiMOS spin qubit
experiments
Optical Chirality Flux as a Useful Far-Field Probe of Chiral Near Fields
To optimize the interaction
between chiral matter and highly twisted light, quantities that can
help characterize chiral electromagnetic fields near nanostructures
are needed. Here, by analogy with Poynting’s theorem, we formulate
the time-averaged conservation law of optical chirality in lossy dispersive
media and identify the optical chirality flux as an ideal far-field
observable for characterizing chiral optical near fields. Bounded
by the conservation law, we show that it provides precise information,
unavailable from circular dichroism spectroscopy, on the magnitude
and handedness of highly twisted fields near nanostructures
Probing Low-Frequency Charge Noise in Few-Electron CMOS Quantum Dots
International audienceCharge noise is one of the main sources of environmental decoherence for spin qubits in silicon, presenting a major obstacle in the path towards highly scalable and reproducible qubit fabrication. Here we demonstrate in-depth characterization of the charge noise environment experienced by a quantum dot in a CMOS-fabricated silicon nanowire. We probe the charge noise for different quantum dot configurations, finding that it is possible to tune the charge noise over two orders of magnitude, ranging from 1μeV2/Hz to 100μeV2/Hz. In particular, we show that the top interface and the reservoirs are the main sources of charge noise, and their effect can be mitigated by controlling the quantum dot extension. Additionally, we demonstrate a method for the measurement of the charge noise experienced by a quantum dot in the few-electron regime. We measure a comparatively high charge noise value of 40μeV2/Hz at the first electron, and demonstrate that the charge noise is highly dependent on the electron occupancy of the quantum dot
Parity and Singlet-Triplet High-Fidelity Readout in a Silicon Double Quantum Dot at 0.5 K
Pauli-spin-blockade (PSB) measurements have so far achieved the highest fidelity of spin readout in semiconductor quantum dots, overcoming the 99% threshold. Moreover, in contrast to energy-selective readout, PSB is less error prone to thermal energy, an important feature for large-scale architectures that could be operated at temperatures above a few hundreds of millikelvins. In this work, we use rf reflectometry on a single-lead quantum dot to perform charge sensing and to probe the spin state of a double quantum dot at 0.5 K. At this relatively elevated temperature, we characterize both singlet-triplet and parity readout, which are complementary measurements to perform a complete readout of a two-spin system. We demonstrate high-fidelity spin readout with an average fidelity above 99.9 % for a readout time of 20 µs and 99 % for 4 µs. Finally, we succeed in initializing a singlet state in a single dot with a fidelity higher than 99 % and separate the two electrons while retaining the same spin state with a 95.6 % fidelity
Broadband parametric amplification for multiplexed SiMOS quantum dot signals
International audienceSpins in semiconductor quantum dots hold great promise as building blocks of quantum processors. Trapping them in SiMOS transistor-like devices eases future industrial scale fabrication. Among the potentially scalable readout solutions, gate-based dispersive radiofrequency reflectometry only requires the already existing transistor gates to readout a quantum dot state, relieving the need for additional elements. In this effort towards scalability, traveling-wave superconducting parametric amplifiers significantly enhance the readout signal-to-noise ratio (SNR) by reducing the noise below typical cryogenic low-noise amplifiers, while offering a broad amplification band, essential to multiplex the readout of multiple resonators. In this work, we demonstrate a 3GHz gate-based reflectometry readout of electron charge states trapped in quantum dots formed in SiMOS multi-gate devices, with SNR enhanced thanks to a Josephson traveling-wave parametric amplifier (JTWPA). The broad, tunable 2GHz amplification bandwidth combined with more than 10dB ON/OFF SNR improvement of the JTWPA enables frequency and time division multiplexed readout of interdot transitions, and noise performance near the quantum limit. In addition, owing to a design without superconducting loops and with a metallic ground plane, the JTWPA is flux insensitive and shows stable performances up to a magnetic field of 1.2T at the quantum dot device, compatible with standard SiMOS spin qubit experiments
Parity and singlet-triplet high fidelity readout in a silicon double quantum dot at 0.5 K
International audienceWe demonstrate singlet-triplet readout and parity readout allowing to distinguish T0 and the polarized triplet states. We achieve high fidelity spin readout with an average fidelity above for a readout time of s and for s at a temperature of . We initialize a singlet state in a single dot with a fidelity higher than and separate the two electrons while keeping the same spin state with fidelity
Parity and singlet-triplet high fidelity readout in a silicon double quantum dot at 0.5 K
We demonstrate singlet-triplet readout and parity readout allowing to distinguish T0 and the polarized triplet states. We achieve high fidelity spin readout with an average fidelity above for a readout time of s and for s at a temperature of . We initialize a singlet state in a single dot with a fidelity higher than and separate the two electrons while keeping the same spin state with fidelity