arXiv:1901.00426 · npj Quantum Information

Loading a quantum-dot based “Qubyte” register

Christian Volk, Anne-Marije Zwerver, U. Mukhopadhyay, Pieter T. Eendebak, Cornelis Jacobus van Diepen, Juan Pablo Dehollain, Toivo Hensgens, T. Fujita, Christian Reichl, W. Wegscheider, Lieven M. K. Vandersypen

Published Apr 23, 2019• 115 citations

arXiv HTML PDF

Abstract

Abstract Electrostatically defined quantum dot arrays offer a compelling platform for quantum computation and simulation. However, tuning up such arrays with existing techniques becomes impractical when going beyond a handful of quantum dots. Here, we present a method for systematically adding quantum dots to an array one dot at a time, in such a way that the number of electrons on previously formed dots is unaffected. The method allows individual control of the number of electrons on each of the dots, as well as of the interdot tunnel rates. We use this technique to tune up a linear array of eight GaAs quantum dots such that they are occupied by one electron each. This new method overcomes a critical bottleneck in scaling up quantum-dot based qubit registers.

DOI: 10.1038/s41534-019-0146-y

Related papers

Automated tuning of inter-dot tunnel coupling in double quantum dots

Cornelis Jacobus van Diepen, Pieter T. Eendebak, Bruno T. Buijtendorp +5 more

Semiconductor quantum dot arrays defined electrostatically in a 2D electron gas provide a scalable platform for quantum information processing and quantum simulations. For the operation of quantum dot arrays, appropriate voltages need to be applied to the gate electrodes that define the quantum dot potential landscape. Tuning the gate voltages has proven to be a time-consuming task, because of initial electrostatic disorder and capacitive cross-talk effects. Here, we report on the automated tuning of the inter-dot tunnel coupling in gate-defined semiconductor double quantum dots. The automation of the tuning of the inter-dot tunnel coupling is the next step forward in scalable and efficient control of larger quantum dot arrays. This work greatly reduces the effort of tuning semiconductor quantum dots for quantum information processing and quantum simulation.

arXiv:1803.10352Applied Physics LettersJul 16, 201870 citations

Controlled quantum dot array segmentation via highly tunable interdot tunnel coupling

Martin Nurizzo, Baptiste Jadot, Pierre-André Mortemousque +8 more

Recent demonstrations using electron spins stored in quantum dot array as qubits are promising for developing a scalable quantum computing platform. An ongoing effort is, therefore, aiming at the precise control of the quantum dot parameters in larger and larger arrays which represents a complex challenge. Partitioning of the system with the help of the inter-dot tunnel barriers can lead to a simplification for tuning and offers a protection against unwanted charge displacement. In a triple quantum dot system, we demonstrate a nanosecond control of the inter-dot tunnel rate permitting to reach the two extreme regimes, large GHz tunnel coupling, and sub-Hz isolation between adjacent dots. We use this development to isolate a subpart of the array in a metastable configuration while performing charge displacement and readout in the rest of the system. The degree of control over tunnel coupling achieved in a unit cell should motivate future protocol development for tuning, manipulation, and readout including this capability.

arXiv:2207.09235Applied Physics LettersAug 22, 20227 citations

A Three-Dimensional Array of Quantum Dots

Hanifa Tidjani, Dario Denora, Michael Chan +6 more

Quantum dots can confine single electrons or holes to define spin qubits that can be operated with high fidelity. Experimental work has progressed from linear to two-dimensional arrays of quantum dots, enabling qubit interactions that are essential for quantum simulation and computation. Here, we explore architectures beyond planar geometries by constructing quantum dot arrays in three dimensions. We realize an eight-quantum dot system in a silicon-germanium heterostructure comprising two stacked germanium quantum wells, where quantum dots are positioned at the vertices of a cuboid. Using electrostatic gate control, we load a single hole into any of the eight quantum dots. To demonstrate the potential of multilayer quantum dot systems, we show coherent spin control and hopping-induced spin rotations by shuttling between the quantum wells. The ability to extend quantum dot arrays in three dimensions provides opportunities for novel quantum hardware and high-connectivity quantum circuits.

cond-mat.mes-hallCross-listedarXiv:2512.01634Dec 2, 2025

Combining multiplexed gate-based readout and isolated CMOS quantum dot arrays

Pierre Hamonic, Martin Nurizzo, Jayshankar Nath +15 more

Semiconductor quantum dot arrays are a promising platform to perform spin-based error-corrected quantum computation with large numbers of qubits. However, due to the diverging number of possible charge configurations combined with the limited sensitivity of large-footprint charge sensors, achieving single-spin occupancy in each dot in a growing quantum dot array is exceedingly complex. Therefore, to scale-up a spin-based architecture we must change how individual charges are readout and controlled. Here, we demonstrate single-spin occupancy of each dot in a foundry-fabricated array by combining two methods. 1/ Loading a finite number of electrons into the quantum dot array; simplifying electrostatic tuning by isolating the array from the reservoirs. 2/ Deploying multiplex gate-based reflectometry to dispersively probe charge tunneling and spin states without charge sensors or reservoirs. Our isolated arrays probed by embedded multiplex readout can be readily electrostatically tuned. They are thus a viable, scalable approach for spin-based quantum architectures. Large-footprint, low-sensitivity charge sensors hinder scaling semiconductor quantum dot arrays for quantum computation. Here the authors present a potentially scalable approach using multiplexed gate-based readout and operation in a foundry-fabricated quantum dot array, demonstrating single-electron occupancy.

arXiv:2410.02325Nature CommunicationsJul 9, 20254 citations

Ray-based automatic tuning of a single quantum dot in a GaAs/AlGaAs quadruple dot array

Ehsan Alizadeh Kashtiban, Takafumi Fujita, A. Oiwa

Abstract Semiconductor quantum dot arrays, a key platform for spin-based quantum computing, face scalability challenges due to the time-consuming manual tuning of potential landscapes. This paper proposes that combining minimal one-dimensional voltage sweeps with machine learning offers a practical method for automating the tuning of four separate single quantum dots, inspired by the Ray-based Classification framework. Our method successfully tunes single quantum dots in a GaAs quadruple quantum dot device, while reducing the complexity of data acquisition and simplifying the tuning process.

Japanese Journal of Applied PhysicsJan 29, 20251 citation

Controlled quantum dot array segmentation and complete two-electron spin state readout

Martin Nurizzo

Spin qubits in semiconductor quantum circuits have been identified as a compelling platform for large scale quantum computing. Today an ongoing effort of the community is aiming at the scaling of such systems by filling larger and larger arrays. In this context the development of tuning and readout protocols allowing to reduce the inherent complexity of such systems seems to be a necessity.In the first part of my thesis, I demonstrate array partitioning of a linear triple quantum dot defined in a AlGaAs/GaAs heterostructure via a highly tunable interdot tunnel coupling. This allows us to operate independently smaller sections of the array which reduces the number of available charge states for the system and therefore reduces its complexity during the tuning.The second part of my thesis is focused on reducing the hardware overhead necessary to extract information during the readout of the spin qubits. In semiconductor spin qubits, high fidelity read-out is obtained through Pauli spin blockade in a double quantum dot with two electrons probed by a local electrometer. One electron is the qubit, the second is the ancilla and only one bit of information is extracted. To obtain the full two-bit information of the two-electron spin states, more quantum hardware is necessary (either dots, electrometers, or reservoirs).Based on an original protocol, I develop in this thesis a complete single-shot read-out procedure for two-electron spin states in a double quantum dot discriminating between S, T0, T+ and T-. It uses successively three distinct spin-to-charge conversion protocols interleaved with charge configuration measurements. The strategy is based on four novel experimental achievements:First, the control from the GHz to sub-Hz regime of the interdot tunnel coupling at the nanosecond timescale.Second, the separation of the spin-to-charge conversion and the charge read-out in the voltage gate space.Third, the suppression of spin relaxation process during the read-out procedure.Finally, the repetition of three distinct spin-to-charge conversion protocols.The read-out procedure is tested on various initialized populations and implemented in more complex spin manipulation sequences to assess its validity.

Jan 16, 20230 citations