I am an active experimental physicist with a bachelor's degree in Electronic Engineering, carrying out research in the field of quantum technologies. I obtained my PhD at the University of New South Wales operating qubit devices based on single-atom spins from impurities in silicon. I then moved to TU Delft as a Postdoc performing quantum simulations with quantum dot arrays in GaAs. In my current Chancellor's Postdoc Fellowship appointment I am performing quantum simulations of light-matter interaction using superconducting circuits.
Prizes and awards:
- 2016 New Journal of Physics Early Career Award. Runner-up.
- 2014 UNSW Faculty of Engineering The Malcolm Chaikin Prize for Research Excellence in Engineering.
- 2013 UNSW Faculty of Engineering Dean’s Award for Research Excellence. Winner in the category “Digital World”.
- 2011 IEEE Technologies of the Future Poster Competition. Winner in the category “Towards Miniaturisation”.
- Reviewer for Physical Review Letters / A / B, Scientific Reports, Journal of Physics Communications
- Member of the editorial board of Journal of Physics Communications
Can supervise: YES
Experimental research in circuit quantum electrodynamics. Exploring the limits of digital quantum simulations of the Rabi model.
- Quantum Physics 68413 - Lecturer and tutor
Dehollain, JP, Mukhopadhyay, U, Michal, VP, Wang, Y, Wunsch, B, Reichl, C, Wegscheider, W, Rudner, MS, Demler, E & Vandersypen, LMK 2020, 'Nagaoka ferromagnetism observed in a quantum dot plaquette', NATURE, vol. 579, no. 7800, pp. 528-533.View/Download from: Publisher's site
Pateras, A, Carnis, J, Mukhopadhyay, U, Richard, MI, Leake, SJ, Schülli, TU, Reichl, C, Wegscheider, W, Dehollain, JP, Vandersypen, LMK & Evans, PG 2019, 'Electrode-induced lattice distortions in GaAs multi-quantum-dot arrays', Journal of Materials Research, vol. 34, no. 8, pp. 1291-1301.View/Download from: Publisher's site
Copyright © Materials Research Society 2019. Increasing the number of quantum bits while preserving precise control of their quantum electronic properties is a significant challenge in materials design for the development of semiconductor quantum computing devices. Semiconductor heterostructures can host multiple quantum dots that are electrostatically defined by voltages applied to an array of metallic nanoelectrodes. The structural distortion of multiple-quantum-dot devices due to elastic stress associated with the electrodes has been difficult to predict because of the large micrometer-scale overall sizes of the devices, the complex spatial arrangement of the electrodes, and the sensitive dependence of the magnitude and spatial variation of the stress on processing conditions. Synchrotron X-ray nanobeam Bragg diffraction studies of a GaAs/AlGaAs heterostructure reveal the magnitude and nanoscale variation of these distortions. Investigations of individual linear electrodes reveal lattice tilts consistent with a 28-MPa compressive residual stress in the electrodes. The angular magnitude of the tilts varies by up to 20% over distances of less than 200 nm along the length of the electrodes, consistent with heterogeneity in the metal residual stress. A similar variation of the crystal tilt is observed in multiple-quantum-dot devices, due to a combination of the variation of the stress and the complex electrode arrangement. The heterogeneity in particular can lead to significant challenges in the scaling of multiple-quantum-dot devices due to differences between the charging energies of dots and uncertainty in the potential energy landscape. Alternatively, if incorporated in design, stress presents a new degree of freedom in device fabrication.
Volk, C, Zwerver, AMJ, Mukhopadhyay, U, Eendebak, PT, van Diepen, CJ, Dehollain, JP, Hensgens, T, Fujita, T, Reichl, C, Wegscheider, W & Vandersypen, LMK 2019, 'Loading a quantum-dot based “Qubyte” register', npj Quantum Information, vol. 5, no. 1.View/Download from: Publisher's site
© 2019, The Author(s). 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.
Wang, Y, Dehollain, JP, Liu, F, Mukhopadhyay, U, Rudner, MS, Vandersypen, LMK & Demler, E 2019, 'Ab initio exact diagonalization simulation of the Nagaoka transition in quantum dots', Physical Review B, vol. 100, no. 15.View/Download from: Publisher's site
© 2019 American Physical Society. Recent progress of quantum simulators provides insight into the fundamental problems of strongly correlated systems. To adequately assess the accuracy of these simulators, the precise modeling of the many-body physics, with accurate model parameters, is crucially important. In this paper, we employed an ab initio exact diagonalization framework to compute the correlated physics of a few electrons in artificial potentials. We apply this approach to a quantum-dot system and study the magnetism of the correlated electrons, obtaining good agreement with recent experimental measurements in a plaquette. Through control of dot potentials and separation, including geometric manipulation of tunneling, we examine the Nagaoka transition and determine the robustness of the ferromagnetic state. While the Nagaoka theorem considers only a single-band Hubbard model, in this work we perform extensive ab initio calculations that include realistic multiorbital conditions in which the level splitting is smaller than the interactions. This simulation complements the experiments and provides insight into the formation of ferromagnetism in correlated systems. More generally, our calculation sets the stage for further theoretical analysis of analog quantum simulators at a quantitative level.
Li, R, Petit, L, Franke, DP, Dehollain, JP, Helsen, J, Steudtner, M, Thomas, NK, Yoscovits, ZR, Singh, KJ, Wehner, S, Vandersypen, LMK, Clarke, JS & Veldhorst, M 2018, 'A crossbar network for silicon quantum dot qubits.', Science advances, vol. 4, no. 7.View/Download from: Publisher's site
The spin states of single electrons in gate-defined quantum dots satisfy crucial requirements for a practical quantum computer. These include extremely long coherence times, high-fidelity quantum operation, and the ability to shuttle electrons as a mechanism for on-chip flying qubits. To increase the number of qubits to the thousands or millions of qubits needed for practical quantum information, we present an architecture based on shared control and a scalable number of lines. Crucially, the control lines define the qubit grid, such that no local components are required. Our design enables qubit coupling beyond nearest neighbors, providing prospects for nonplanar quantum error correction protocols. Fabrication is based on a three-layer design to define qubit and tunnel barrier gates. We show that a double stripline on top of the structure can drive high-fidelity single-qubit rotations. Self-aligned inhomogeneous magnetic fields induced by direct currents through superconducting gates enable qubit addressability and readout. Qubit coupling is based on the exchange interaction, and we show that parallel two-qubit gates can be performed at the detuning-noise insensitive point. While the architecture requires a high level of uniformity in the materials and critical dimensions to enable shared control, it stands out for its simplicity and provides prospects for large-scale quantum computation in the near future.
Muhonen, JT, Dehollain, JP, Laucht, A, Simmons, S, Kalra, R, Hudson, FE, Dzurak, AS, Morello, A, Jamieson, DN, McCallum, JC & Itoh, KM 2018, 'Coherent control via weak measurements in P 31 single-atom electron and nuclear spin qubits', Physical Review B, vol. 98, no. 15.View/Download from: Publisher's site
© 2018 American Physical Society. The understanding of weak measurements and interaction-free measurements has greatly expanded the conceptual and experimental toolbox to explore the quantum world. Here we demonstrate single-shot variable-strength weak measurements of the electron and nuclear spin states of a P31 single-atom donor in silicon. We first show how the partial collapse of the nuclear spin due to measurement can be used to coherently rotate the spin to a desired pure state. We explicitly demonstrate that phase coherence is preserved with high fidelity throughout multiple sequential single-shot weak measurements and that the partial state collapse can be reversed. Second, we use the relation between measurement strength and perturbation of the nuclear state as a physical meter to extract the tunnel rates between the P31 donor and a nearby electron reservoir from data conditioned on observing no tunneling events. Our experiments open avenues to measurement-based state preparation, steering and feedback protocols for spin systems in the solid state, and highlight the fundamental connection between information gain and state modification in quantum mechanics.
Mukhopadhyay, U, Dehollain, JP, Reichl, C, Wegscheider, W & Vandersypen, LMK 2018, 'A 2 × 2 quantum dot array with controllable inter-dot tunnel couplings', Applied Physics Letters, vol. 112, no. 18.View/Download from: Publisher's site
© 2018 Author(s). The interaction between electrons in arrays of electrostatically defined quantum dots is naturally described by a Fermi-Hubbard Hamiltonian. Moreover, the high degree of tunability of these systems makes them a powerful platform to simulate different regimes of the Hubbard model. However, most quantum dot array implementations have been limited to one-dimensional linear arrays. In this letter, we present a square lattice unit cell of 2 × 2 quantum dots defined electrostatically in an AlGaAs/GaAs heterostructure using a double-layer gate technique. We probe the properties of the array using nearby quantum dots operated as charge sensors. We show that we can deterministically and dynamically control the charge occupation in each quantum dot in the single- to few-electron regime. Additionally, we achieve simultaneous individual control of the nearest-neighbor tunnel couplings over a range of 0-40 μeV. Finally, we demonstrate fast (∼1 μs) single-shot readout of the spin state of electrons in the dots through spin-to-charge conversion via Pauli spin blockade. These advances pave the way for analog quantum simulations in two dimensions, not previously accessible in quantum dot systems.
Pateras, A, Park, J, Ahn, Y, Tilka, JA, Holt, MV, Reichl, C, Wegscheider, W, Baart, TA, Dehollain, JP, Mukhopadhyay, U, Vandersypen, LMK & Evans, PG 2018, 'Mesoscopic Elastic Distortions in GaAs Quantum Dot Heterostructures.', Nano Letters, vol. 18, no. 5, pp. 2780-2786.View/Download from: Publisher's site
Quantum devices formed in high-electron-mobility semiconductor heterostructures provide a route through which quantum mechanical effects can be exploited on length scales accessible to lithography and integrated electronics. The electrostatic definition of quantum dots in semiconductor heterostructure devices intrinsically involves the lithographic fabrication of intricate patterns of metallic electrodes. The formation of metal/semiconductor interfaces, growth processes associated with polycrystalline metallic layers, and differential thermal expansion produce elastic distortion in the active areas of quantum devices. Understanding and controlling these distortions present a significant challenge in quantum device development. We report synchrotron X-ray nanodiffraction measurements combined with dynamical X-ray diffraction modeling that reveal lattice tilts with a depth-averaged value up to 0.04° and strain on the order of 10-4 in the two-dimensional electron gas (2DEG) in a GaAs/AlGaAs heterostructure. Elastic distortions in GaAs/AlGaAs heterostructures modify the potential energy landscape in the 2DEG due to the generation of a deformation potential and an electric field through the piezoelectric effect. The stress induced by metal electrodes directly impacts the ability to control the positions of the potential minima where quantum dots form and the coupling between neighboring quantum dots.
Freer, S, Simmons, S, Laucht, A, Muhonen, JT, Dehollain, JP, Kalra, R, Mohiyaddin, FA, Hudson, FE, Itoh, KM, McCallum, JC, Jamieson, DN, Dzurak, AS & Morello, A 2017, 'A single-atom quantum memory in silicon', QUANTUM SCIENCE AND TECHNOLOGY, vol. 2, no. 1.View/Download from: Publisher's site
Laucht, A, Kalra, R, Simmons, S, Dehollain, JP, Muhonen, JT, Mohiyaddin, FA, Freer, S, Hudson, FE, Itoh, KM, Jamieson, DN, McCallum, JC, Dzurak, AS & Morello, A 2017, 'A dressed spin qubit in silicon', NATURE NANOTECHNOLOGY, vol. 12, no. 1, pp. 61-66.View/Download from: Publisher's site
Dehollain, JP, Muhonen, JT, Blume-Kohout, R, Rudinger, KM, Gamble, JK, Nielsen, E, Laucht, A, Simmons, S, Kalra, R, Dzurak, AS & Morello, A 2016, 'Optimization of a solid-state electron spin qubit using gate set tomography', NEW JOURNAL OF PHYSICS, vol. 18.View/Download from: Publisher's site
Dehollain, JP, Simmons, S, Muhonen, JT, Kalra, R, Laucht, A, Hudson, F, Itoh, K, Jamieson, DN, McCallum, JC, Dzurak, AS & Morello, A 2016, 'Bell's inequality violation with spins in silicon', NATURE NANOTECHNOLOGY, vol. 11, no. 3, pp. 242-+.View/Download from: Publisher's site
Kalra, R, Laucht, A, Dehollain, JP, Bar, D, Freer, S, Simmons, S, Muhonen, JT & Morello, A 2016, 'Vibration-induced electrical noise in a cryogen-free dilution refrigerator: Characterization, mitigation, and impact on qubit coherence', REVIEW OF SCIENTIFIC INSTRUMENTS, vol. 87, no. 7.View/Download from: Publisher's site
Laucht, A, Simmons, S, Kalra, R, Tosi, G, Dehollain, JP, Muhonen, JT, Freer, S, Hudson, FE, Itoh, KM, Jamieson, DN, McCallum, JC, Dzurak, AS & Morello, A 2016, 'Breaking the rotating wave approximation for a strongly driven dressed single-electron spin', PHYSICAL REVIEW B, vol. 94, no. 16.View/Download from: Publisher's site
Laucht, A, Muhonen, JT, Mohiyaddin, FA, Kalra, R, Dehollain, JP, Freer, S, Hudson, FE, Veldhorst, M, Rahman, R, Klimeck, G, Itoh, KM, Jamieson, DN, McCallum, JC, Dzurak, AS & Morello, A 2015, 'Electrically controlling single-spin qubits in a continuous microwave field', SCIENCE ADVANCES, vol. 1, no. 3.View/Download from: Publisher's site
Muhonen, JT, Laucht, A, Simmons, S, Dehollain, JP, Kalra, R, Hudson, FE, Freer, S, Itoh, KM, Jamieson, DN, McCallum, JC, Dzurak, AS & Morello, A 2015, 'Quantifying the quantum gate fidelity of single-atom spin qubits in silicon by randomized benchmarking', JOURNAL OF PHYSICS-CONDENSED MATTER, vol. 27, no. 15.View/Download from: Publisher's site
Veldhorst, M, Yang, CH, Hwang, JCC, Huang, W, Dehollain, JP, Muhonen, JT, Simmons, S, Laucht, A, Hudson, FE, Itoh, KM, Morello, A & Dzurak, AS 2015, 'A two-qubit logic gate in silicon', NATURE, vol. 526, no. 7573, pp. 410-414.View/Download from: Publisher's site
Dehollain, JP, Muhonen, JT, Tan, KY, Saraiva, A, Jamieson, DN, Dzurak, AS & Morello, A 2014, 'Single-Shot Readout and Relaxation of Singlet and Triplet States in Exchange-Coupled P-31 Electron Spins in Silicon', PHYSICAL REVIEW LETTERS, vol. 112, no. 23.View/Download from: Publisher's site
Laucht, A, Kalra, R, Muhonen, JT, Dehollain, JP, Mohiyaddin, FA, Hudson, F, McCallum, JC, Jamieson, DN, Dzurak, AS & Morello, A 2014, 'High-fidelity adiabatic inversion of a P-31 electron spin qubit in natural silicon', APPLIED PHYSICS LETTERS, vol. 104, no. 9.View/Download from: Publisher's site
Muhonen, JT, Dehollain, JP, Laucht, A, Hudson, FE, Kalra, R, Sekiguchi, T, Itoh, KM, Jamieson, DN, McCallum, JC, Dzurak, AS & Morello, A 2014, 'Storing quantum information for 30 seconds in a nanoelectronic device', NATURE NANOTECHNOLOGY, vol. 9, no. 12, pp. 986-991.View/Download from: Publisher's site
Newall, AT & Dehollain, JP 2014, 'The cost-effectiveness of influenza vaccination in elderly Australians: An exploratory analysis of the vaccine efficacy required', VACCINE, vol. 32, no. 12, pp. 1323-1325.View/Download from: Publisher's site
Pla, JJ, Mohiyaddin, FA, Tan, KY, Dehollain, JP, Rahman, R, Klimeck, G, Jamieson, DN, Dzurak, AS & Morello, A 2014, 'Coherent Control of a Single Si-29 Nuclear Spin Qubit', PHYSICAL REVIEW LETTERS, vol. 113, no. 24.View/Download from: Publisher's site
Veldhorst, M, Hwang, JCC, Yang, CH, Leenstra, AW, de Ronde, B, Dehollain, JP, Muhonen, JT, Hudson, FE, Itoh, KM, Morello, A & Dzurak, AS 2014, 'An addressable quantum dot qubit with fault-tolerant control-fidelity', NATURE NANOTECHNOLOGY, vol. 9, no. 12, pp. 981-985.View/Download from: Publisher's site
Dehollain, JP, Pla, JJ, Siew, E, Tan, KY, Dzurak, AS & Morello, A 2013, 'Nanoscale broadband transmission lines for spin qubit control', NANOTECHNOLOGY, vol. 24, no. 1.View/Download from: Publisher's site
Newall, AT, Dehollain, JP, Creighton, P, Beutels, P & Wood, JG 2013, 'Understanding the Cost-Effectiveness of Influenza Vaccination in Children: Methodological Choices and Seasonal Variability', PHARMACOECONOMICS, vol. 31, no. 8, pp. 693-702.View/Download from: Publisher's site
Pla, JJ, Tan, KY, Dehollain, JP, Lim, WH, Morton, JJL, Zwanenburg, FA, Jamieson, DN, Dzurak, AS & Morello, A 2013, 'High-fidelity readout and control of a nuclear spin qubit in silicon', NATURE, vol. 496, no. 7445, pp. 334-338.View/Download from: Publisher's site
Newall, AT, Dehollain, JP & Wood, JG 2012, 'Under-explored assumptions in influenza vaccination models: Implications for the universal vaccination of children', VACCINE, vol. 30, no. 39, pp. 5776-5781.View/Download from: Publisher's site
Boter, JM, Dehollain, JP, Van DIjk, JPG, Hensgens, T, Versluis, R, Clarke, JS, Veldhorst, M, Sebastiano, F & Vandersypen, LMK 2019, 'A sparse spin qubit array with integrated control electronics', Technical Digest - International Electron Devices Meeting, IEDM.View/Download from: Publisher's site
© 2019 IEEE. Current implementations of quantum computers suffer from large numbers of control lines per qubit, becoming unmanageable with system scale up. Here, we discuss a sparse spin-qubit architecture featuring integrated control electronics significantly reducing the off-chip wire count. This quantum-classical hardware integration closes the feasibility gap towards a CMOS quantum computer.
Pillarisetty, R, Thomas, N, George, HC, Singh, K, Roberts, J, Lampert, L, Amin, P, Watson, TF, Zheng, G, Torres, J, Metz, M, Kotlyar, R, Keys, P, Boter, JM, Dehollain, JP, Droulers, G, Eenink, G, Li, R, Massa, L, Sabbagh, D, Samkharadze, N, Volk, C, Wuetz, BP, Zwerver, AM, Veldhorst, M, Scappucci, G, Vandersypen, LMK & Clarke, JS 2018, 'Qubit Device Integration Using Advanced Semiconductor Manufacturing Process Technology', Technical Digest - International Electron Devices Meeting, IEDM, IEEE International Electron Devices Meeting, IEEE, USA, pp. 6.3.1-6.3.4.View/Download from: Publisher's site
© 2018 IEEE. Quantum computing's value proposition of an exponential speedup in computing power for certain applications has propelled a vast array of research across the globe. While several different physical implementations of device level qubits are being investigated, semiconductor spin qubits have many similarities to scaled transistors. In this article, we discuss the device/integration of full 300mm based spin qubit devices. This includes the development of (i) a 28 Si epitaxial module ecosystem for growing isotopically pure substrates with among the best Hall mobility at these oxide thicknesses, (ii) a custom 300mm qubit testchip and integration/device line, and (iii) a novel dual nested gate integration process for creating quantum dots.
Clarke, JS, Thomas, N, Roberts, J, Pilliarisetty, R, Yoscovits, Z, Caudillo, R, George, H, Singh, KJ, Michalak, D, Amin, P, Mei, A, Bruno, A, Poletto, S, Boter, J, Droulers, G, Kalhor, N, Samkharadze, N, Dehollain, JP, Yeoh, L, Sammak, A, Scappucci, G, Veldhorst, M, DiCarlo, L & Vandersypen, LMK 2016, 'Quantum Computing Within the Framework of Advanced Semiconductor Manufacturing', 2016 IEEE INTERNATIONAL ELECTRON DEVICES MEETING (IEDM), 62nd Annual IEEE International Electron Devices Meeting (IEDM), IEEE, San Francisco, CA.
Morello, A, Dehollain, JP, Kalra, R, Laucht, A, Mohiyaddin, FA, Muhonen, JT, Pla, JJ, Jamieson, DN, McCallum, JC & Dzurak, AS 2014, 'Single-atom spin qubits in silicon', 2014 Conference on Optoelectronic and Microelectronic Materials and Devices, COMMAD 2014, pp. 198-199.View/Download from: Publisher's site
© 2014 IEEE. The electron and nuclear spins of a single phosphorus atom in silicon constitute highly coherent, readable and addressable qubits embedded within the most important material in the microelectronics industry. This paper reports the current state-of-the art in the field of single-atom spin qubits.