Quantum Motion attends APS March Meeting 2024: Who, What, Where, and When

Three team members are heading to Minneapolis to attend this year’s American Physical Society’s (APS) March Meeting. The APS March Meeting brings together scientists and students from around the world to connect and collaborate across academia, industry, and major labs.

Quantum Motion team members will be presenting three talks at this year’s conference. Find out who is speaking, when and where below:

B46.00011: RF Diode Thermometry – Pushing the limits of cryogenic temperature sensing

Monday 4 March 2024, 1:54PM (GMT-6), Room 200AB

Tom Swift, Quantum Engineer

Addressing and operating the large number of qubits needed for fault-tolerant quantum computing requires the integration of classical circuitry close to or on the same chip as qubits operating at cryogenic temperatures. These classical circuits dissipate power which may affect qubit operation. Experimental tools to probe these static and dynamic effects are therefore of interest to the field and will lead to a better understanding of the recent temperature-dependence observed in semiconductor spin-qubit systems. Previously it has been shown that diode thermometry is the most sensitive cryogenic thermometry technique native to CMOS devices. In this work, we further increase the sensitivity of diode thermometry by using radiofrequency reflectometry (RF) techniques and demonstrate state-of-the-art cryogenic temperature sensing capabilities, maintaining sensitivity down to 20mK. The technique allows us to conduct pulsed heating experiments with a resolution of <1µs commensurate with that achieved in semiconductor qubit architectures. The ability to probe at high frequency provides insight into the dynamic temperature behavior of the chip as a result of both localized (on-chip) and global (PCB) level heating. This technique will allow future experimental studies of quantum thermodynamics in nanoelectronic systems as well as increase our understanding of dynamic power dissipation in cryoelectronic and quantum circuits.

This work received support from the UK Engineering and Physical Sciences Research Council (EPSRC) through the Centre for Doctoral Training in Delivering Quantum Technologies [EP/S021582/1] and a UKRI Future Leaders Fellowship [MR/V023284/1].

S46.00009: High-fidelity dispersive spin readout in a scalable unit cell of silicon quantum dots

Thursday 7 March, 2024, 10.00AM (GMT-6), Room 200AB

Constance Lainé, Quantum Engineer

Planar MOS multi-gate technology is one of the leading approaches to silicon-based quantum computing. For readout of spin qubits, dispersive sensing offers the potential of scalable unit cells by avoiding the need for multiple charge reservoirs. So far, demonstrations of planar MOS quantum dots have been restricted to architectures where sensors are co-linear with the qubit array, limiting scalability. Achieving readout fidelity at the level of control operations has also remained challenging. In this work, we address both limitations: we demonstrate single-shot spin readout with fidelity above 99.9% measured in 200 us in a planar MOS quantum dot array fabricated using a 300mm wafer process. We use a single electron box (SEB) to measure the two-electron spin state of a double quantum dot using Pauli spin blockade. The sensor and qubit dots are placed in parallel channels of a bilinear array of quantum dots, forming a compact unit cell. The high fidelity is achieved thanks to the tunability of the structure that allows (i) optimization of the tunnel rate of the SEB for enhanced signal and (ii) tuning of the coupling between the double quantum dots using a J-gate, leading to an enhancement of the singlet-triplet relaxation time from 4 us to 0.5 s. Overall, this work demonstrates sensing in a compact unit cell with state-of-the art fidelity, providing a path to scalable high-connectivity bilinear qubit arrays.

This work received support from the UK Engineering and Physical Sciences Research Council [EP/L015242/1, EP/S021582/1] and a UKRI Future Leaders Fellowship [MR/V023284/1].

W46.00007: Gate-based spin readout in planar Si-MOS quantum dots using an off-chip microwave resonator

Thursday 7 March 2024, 4.12PM (GMT-6), Room 200AB

Frédéric Schlattner, Quantum Engineer

Planar Si-MOS technology provides a promising platform to build scalable two-dimensional arrays with nearest neighbour connectivity needed to implement, efficiently, the surface code. Reflectometry techniques can perform spin read-out through the gate and are therefore a promising approach to read out dense two-dimensional qubit arrays without compromising the qubit connectivity. However, in planar technologies, efforts to achieve high-fidelity gate-based read-out have been hindered by multiple factors, such as lower gate lever arms and parasitic two-dimensional electron gases in accumulation mode devices. In this work, we interface the quantum device fabricated on a 300mm wafer with a newly developed high-impedance off-chip resonator at 1.32 GHz. With our approach, we demonstrate dispersive detection of an inter-dot charge transition with a state-of-the-art signal-to-noise ratio of 1 in 100 us in planar Si-MOS and perform singlet-triplet spin readout via Pauli spin blockade.

This work received support from the UK Engineering and Physical Sciences Research Council [EP/L015242/1, EP/S021582/1], the European Union’s Horizon 2020 programme [951852], and a UKRI Future Leaders Fellowship [MR/V023284/1].