arXiv subjects

Marc Sanquer

Publications and source records attributed to Marc Sanquer.

At least 19 recordsLinked to original sources

arXiv2020

Dispersively probed microwave spectroscopy of a silicon hole double quantum dot

Owing to ever increasing gate fidelities and to a potential transferability to industrial CMOS technology, silicon spin qubits have become a compelling option in the strive for quantum computation. In a scalable architecture, each spin qubit will have to be finely tuned and its operating conditions accurately determined. In this prospect, spectroscopic tools compatible with a scalable device layout are of primary importance. Here we report a two-tone spectroscopy technique providing access to the spin-dependent energy-level spectrum of a hole double quantum dot defined in a split-gate silicon device. A first GHz-frequency tone drives electric-dipole spin resonance enabled by the valence-band spin-orbit coupling. A second lower-frequency tone (approximately 500 MHz) allows for dispersive readout via rf-gate reflectometry. We compare the measured dispersive response to the linear response calculated in an extended Jaynes-Cummings model and we obtain characteristic parameters such as g-factors and tunnel/spin-orbit couplings for both even and odd occupation.

cond-mat.mes-hall↗

arXiv2020

Charge detection in an array of CMOS quantum dots

The recent development of arrays of quantum dots in semiconductor nanostructures highlights the progress of quantum devices toward large scale. However, how to realize such arrays on a scalable platform such as silicon is still an open question. One of the main challenge resides in the detection of charges within the array. It is a prerequisite functionality to initialize a desired charge state and readout spins through spin-to-charge conversion mechanisms. In this paper, we use two methods based on either a single-lead charge detector, or a reprogrammable single electron transistor. Thanks to these methods, we study the charge dynamics and sensitivity by performing single shot detection of the charge. Finally, we can probe the charge stability at any node of a linear array and assess the Coulomb disorder in the structure. We find an electrochemical potential fluctuation induced by charge noise comparable to that reported in other silicon quantum dots.

cond-mat.mes-hall↗

arXiv2019

All-Electrical Control of an Electron Spin/Valley Quantum Bit in SOI CMOS Technology

We fabricated Quantum Dot (QD) devices using a standard SOI CMOS process flow, and demonstrated that the spin of confined electrons could be controlled via a local electrical-field excitation, owing to inter-valley spin-orbit coupling. We discuss that modulating the confinement geometry via an additional electrode may enable switching a quantum bit (qubit) between an electrically-addressable valley configuration and a protected spin configuration. This proposed scheme bears relevance to improve the trade-off between fast operations and slow decoherence for quantum computing on a Si qubit platform. Finally, we evoke the impact of process-induced variability on the operating bias range.

cond-mat.mes-hall↗

arXiv2018

Gate-Based High Fidelity Spin Read-out in a CMOS Device

The engineering of electron spin qubits in a compact unit cell embedding all quantum functionalities is mandatory for large scale integration. In particular, the development of a high-fidelity and scalable spin readout method remains an open challenge. Here we demonstrate high-fidelity and robust spin readout based on gate reflectometry in a CMOS device comprising one qubit dot and one ancillary dot coupled to an electron reservoir to perform readout. This scalable method allows us to read out a spin with a fidelity above 99% for 1 ms integration time. To achieve such fidelity, we exploit a latched spin blockade mechanism that requires electron exchange between the ancillary dot and the reservoir. We show that the demonstrated high read-out fidelity is fully preserved up to 0.5 K. This results holds particular relevance for the future co-integration of spin qubits and classical control electronics.

cond-mat.mes-hall↗

arXiv2018

Collective energy gap of preformed Cooper-pairs in disordered superconductors

In most superconductors the transition to the superconducting state is driven by the binding of electrons into Cooper-pairs. The condensation of these pairs into a single, phase coherent, quantum state takes place concomitantly with their formation at the transition temperature, $T_c$. A different scenario occurs in some disordered, amorphous, superconductors: Instead of a pairing-driven transition, incoherent Cooper pairs first pre-form above $T_c$, causing the opening of a pseudogap, and then, at $T_c$, condense into the phase coherent superconducting state. Such a two-step scenario implies the existence of a new energy scale, $\Delta_{c}$, driving the collective superconducting transition of the preformed pairs. Here we unveil this energy scale by means of Andreev spectroscopy in superconducting thin films of amorphous indium oxide. We observe two Andreev conductance peaks at $\pm \Delta_{c}$ that develop only below $T_c$ and for highly disordered films on the verge of the transition to insulator. Our findings demonstrate that amorphous superconducting films provide prototypical disordered quantum systems to explore the collective superfluid transition of preformed Cooper-pairs pairs.

cond-mat.supr-con↗

arXiv2018

Strongly correlated charge transport in silicon MOSFET quantum dots

Quantum shot noise probes the dynamics of charge transfers through a quantum conductor, reflecting whether quasiparticles flow across the conductor in a steady stream, or in syncopated bursts. We have performed high-sensitivity shot noise measurements in a quantum dot obtained in a silicon metal-oxide-semiconductor field-effect transistor. The quality of our device allows us to precisely associate the different transport regimes and their statistics with the internal state of the quantum dot. In particular, we report on large current fluctuations in the inelastic cotunneling regime, corresponding to different highly-correlated, non-Markovian charge transfer processes. We have also observed unusually large current fluctuations at low energy in the elastic cotunneling regime, the origin of which remains to be fully investigated.

cond-mat.mes-hall↗

arXiv2017

Electrical spin driving by $g$-matrix modulation in spin-orbit qubits

In a semiconductor spin qubit with sizable spin-orbit coupling, coherent spin rotations can be driven by a resonant gate-voltage modulation. Recently, we have exploited this opportunity in the experimental demonstration of a hole spin qubit in a silicon device. Here we investigate the underlying physical mechanisms by measuring the full angular dependence of the Rabi frequency as well as the gate-voltage dependence and anisotropy of the hole $g$-factors. We show that a $g$-matrix formalism can simultaneously capture and discriminate the contributions of two mechanisms so far independently discussed in the literature: one associated with the modulation of the $g$ factors, and measurable by Zeeman energy spectroscopy, the other not. Our approach has a general validity and can be applied to the analysis of other types of spin-orbit qubits.

cond-mat.mes-hall↗

arXiv2017

Electrically driven electron spin resonance mediated by spin-valley-orbit coupling in a silicon quantum dot

The ability to manipulate electron spins with voltage-dependent electric fields is key to the operation of quantum spintronics devices, such as spin-based semiconductor qubits. A natural approach to electrical spin control exploits the spin-orbit coupling (SOC) inherently present in all materials. So far, this approach could not be applied to electrons in silicon, due to their extremely weak SOC. Here we report an experimental realization of electrically driven electron-spin resonance in a silicon-on-insulator (SOI) nanowire quantum dot device. The underlying driving mechanism results from an interplay between SOC and the multi-valley structure of the silicon conduction band, which is enhanced in the investigated nanowire geometry. We present a simple model capturing the essential physics and use tight-binding simulations for a more quantitative analysis. We discuss the relevance of our findings to the development of compact and scalable electron-spin qubits in silicon.

cond-mat.mes-hall↗

arXiv2016

Level spectrum and charge relaxation in a silicon double quantum dot probed by dual-gate reflectometry

We report on dual-gate reflectometry in a metal-oxide-semiconductor double-gate silicon transistor operating at low temperature as a double quantum dot device. The reflectometry setup consists of two radio-frequency resonators respectively connected to the two gate electrodes. By simultaneously measuring their dispersive response, we obtain the complete charge stability diagram of the device. Charge transitions between the two quantum dots and between each quantum dot and either the source or the drain contact are detected through phase shifts in the reflected radio-frequency signals. At finite bias, reflectometry allows probing charge transitions to excited quantum-dot states thereby enabling direct access to the energy level spectra of the quantum dots. Interestingly, we find that in the presence of charge transport across the two dots the reflectometry signatures of interdot transitions display a dip-peak structure containing quantitative information on the charge relaxation rates in the double quantum dot.

cond-mat.mes-hall↗

arXiv2016

Pauli Blockade in a Few-Hole PMOS Double Quantum Dot limited by Spin-Orbit Interaction

We report on hole compact double quantum dots fabricated using conventional CMOS technology. We provide evidence of Pauli spin blockade in the few hole regime which is relevant to spin qubit implementations. A current dip is observed around zero magnetic field, in agreement with the expected behavior for the case of strong spin-orbit. We deduce an intradot spin relaxation rate $\approx$120\,kHz for the first holes, an important step towards a robust hole spin-orbit qubit.

cond-mat.mes-hall↗

arXiv2016

Dopant-controlled single-electron pumping through a metallic island

We investigate a hybrid metallic island / single dopant electron pump based on fully-depleted silicon on insulator technology. Electron transfer between the central metallic island and the leads is controlled by resonant tunneling through single phosphorus dopants in the barriers. Top gates above the barriers are used control the resonance conditions. Applying radio frequency signals to the gates, non-adiabatic quantized electron pumping is achieved. A simple deterministic model is presented and confirmed by comparing measurements with simulations.

cond-mat.mes-hall↗

arXiv2014

Control of the ionization state of 3 single donor atoms in silicon

By varying the gate and substrate voltage in a short silicon-on-insulator trigate field effect transistor we control the ionization state of three arsenic donors. We obtain a good quantitative agreement between 3D electrostatic simulation and experiment for the control voltage at which the ionization takes place. It allows us observing the three doubly occupied states As- at strong electric field in the presence of nearby source-drain electrodes.

cond-mat.mes-hall↗

arXiv2012

Detection of a large valley-orbit splitting in silicon with two-donor spectroscopy

We measure a large valley-orbit splitting for shallow isolated phosphorus donors in a silicon gated nanowire. This splitting is close to the bulk value and well above previous reports in silicon nanostructures. It was determined using a double dopant transport spectroscopy which eliminates artifacts induced by the environment. Quantitative simulations taking into account the position of the donors with respect to the Si/SiO$_2$ interface and electric field in the wire show that the values found are consistent with the device geometry.

cond-mat.mes-hall↗

arXiv2012

Few Electron Limit of n-type Metal Oxide Semiconductor Single Electron Transistors

We report electronic transport on n-type silicon Single Electron Transistors (SETs) fabricated in Complementary Metal Oxide Semiconductor (CMOS) technology. The n-MOSSETs are built within a pre-industrial Fully Depleted Silicon On Insulator (FDSOI) technology with a silicon thickness down to 10 nm on 200 mm wafers. The nominal channel size of 20 $\times$ 20 nm$^{2}$ is obtained by employing electron beam lithography for active and gate levels patterning. The Coulomb blockade stability diagram is precisely resolved at 4.2 K and it exhibits large addition energies of tens of meV. The confinement of the electrons in the quantum dot has been modeled by using a Current Spin Density Functional Theory (CS-DFT) method. CMOS technology enables massive production of SETs for ultimate nanoelectronics and quantum variables based devices.

cond-mat.mes-hall↗

arXiv2012

A tunable, dual mode field-effect or single electron transistor

A dual mode device behaving either as a field-effect transistor or a single electron transistor (SET) has been fabricated using silicon-on-insulator metal oxide semiconductor technology. Depending on the back gate polarisation, an electron island is accumulated under the front gate of the device (SET regime), or a field-effect transistor is obtained by pinching off a bottom channel with a negative front gate voltage. The gradual transition between these two cases is observed. This dual function uses both vertical and horizontal tunable potential gradients in non-overlapped silicon-on-insulator channel.

cond-mat.mes-hall↗

arXiv2011

Joule-assisted silicidation for short-channel silicon nanowire devices

We report on a technique enabling electrical control of the contact silicidation process in silicon nanowire devices. Undoped silicon nanowires were contacted by pairs of nickel electrodes and each contact was selectively silicided by means of the Joule effect. By a realtime monitoring of the nanowire electrical resistance during the contact silicidation process we were able to fabricate nickel-silicide/silicon/nickel- silicide devices with controlled silicon channel length down to 8 nm.

cond-mat.mes-hall↗

arXiv2010

Intrinsic and doped coupled quantum dots created by local modulation of implantation in a silicon nanowire

We present a systematic study of various ways (top gates, local doping, substrate bias) to fabricate and tune multi-dot structures in silicon nanowire multigate MOSFETs (metal-oxide-semiconductor field-effect transistors). The carrier concentration profile of the silicon nanowire is a key parameter to control the formation of tunnel barriers and single-electron islands. It is determined both by the doping profile of the nanowire and by the voltages applied to the top gates and to the substrate. Local doping is achieved with the realisation of up to two arsenic implantation steps in combination with gates and nitride spacers acting as a mask. We compare nominally identical devices with different implantations and different voltages applied to the substrate, leading to the realisation of both intrinsic and doped coupled dot structures. We demonstrate devices in which all the tunnel resistances towards the electrodes and between the dots can be independently tuned with the control top gates wrapping the silicon nanowire.

cond-mat.mes-hall↗

arXiv2010

Compact silicon double and triple dots realized with only two gates

We report electronic transport on silicon double and triple dots created with the optimized number of two gates. Using silicon nitride spacers two dots in series are created below two top gates overlapping a silicon nanowire. Coupling between dots is controlled by gate voltages. A third dot is created either by combined action of gate voltages or local doping depending on the spacers length. The main characteristics of the triple dot stability diagram are quantitatively fitted.

cond-mat.mes-hall↗