The germanium quantum information route

Scappucci, Giordano; Kloeffel, Christoph; Zwanenburg, Floris A.; Loss, Daniel; Myronov, Maksym; Zhang, Jian Jun; Franceschi, S. De; Katsaros, Georgios; Veldhorst, Menno

doi:10.1038/s41578-020-00262-z

Cited by 295 publications

(224 citation statements)

References 252 publications

(426 reference statements)

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“…The Ge qubit count has doubled roughly every year and larger systems are on the horizon. The Ge quantum information route 37 is poised to retain many advantages of GaAs and Si while overcoming some of their respective long-standing challenges.…”

Section: Discussionmentioning

confidence: 99%

“…While most studies have focused on electrons, holes in strained Ge/SiGe heterostructures have recently emerged as a compelling platform that offers low disorder, all-electrical qubit control, and avenues for scaling. 37 Ge combines many advantages of Si and GaAs while overcoming most of their limitations. Ge is a CMOS-foundry material and can be isotopically engineered for long quantum coherence.…”

Section: Germaniummentioning

confidence: 99%

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Crystalline materials for quantum computing: Semiconductor heterostructures and topological insulators exemplars

et al. 2021

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High-purity crystalline solid-state materials play an essential role in various technologies for quantum information processing, from qubits based on spins to topological states. New and improved crystalline materials emerge each year and continue to drive new results in experimental quantum science. This article summarizes the opportunities for a selected class of crystalline materials for qubit technologies based on spins and topological states and the challenges associated with their fabrication. We start by describing semiconductor heterostructures for spin qubits in gate-defined quantum dots and benchmark GaAs, Si, and Ge, the three platforms that demonstrated two-qubit logic. We then examine novel topologically nontrivial materials and structures that might be incorporated into superconducting devices to create topological qubits. We review topological insulator thin films and move onto topological crystalline materials, such as PbSnTe, and its integration with Josephson junctions. We discuss advances in novel and specialized fabrication and characterization techniques to enable these. We conclude by identifying the most promising directions where advances in these material systems will enable progress in qubit technology.

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Section: Discussionmentioning

confidence: 99%

Section: Germaniummentioning

confidence: 99%

Crystalline materials for quantum computing: Semiconductor heterostructures and topological insulators exemplars

et al. 2021

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“…The performance analysis of various quantum analogues of classical heat engines serve as a test bed to study different extensions of thermodynamic ideas in the quantum world. With the recent development of quantum information technology [ 51 , 52 , 53 , 54 ] and a number of interesting results, the study of quantum heat engines (QHEs) has drawn much interest. In fact, the past few years witnessed conducive studies exploring how quantum statistics, discreteness of energy levels, quantum adiabaticity, quantum coherence, quantum measurement and entanglement affect the operation of heat engines and cycles in various experimental set-ups, including trapped ions, transmon qubits and more [ 55 , 56 , 57 , 58 , 59 , 60 , 61 , 62 , 63 , 64 , 65 , 66 , 67 , 68 , 69 , 70 , 71 , 72 , 73 , 74 , 75 , 76 , 77 , 78 , 79 , 80 , 81 , 82 , 83 , 84 ].…”

Section: Introductionmentioning

confidence: 99%

Quantum Heat Engines with Complex Working Media, Complete Otto Cycles and Heuristics

Johal

Mehta

2021

Entropy

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Quantum thermal machines make use of non-classical thermodynamic resources, one of which include interactions between elements of the quantum working medium. In this paper, we examine the performance of a quasi-static quantum Otto engine based on two spins of arbitrary magnitudes subject to an external magnetic field and coupled via an isotropic Heisenberg exchange interaction. It has been shown earlier that the said interaction provides an enhancement of cycle efficiency, with an upper bound that is tighter than the Carnot efficiency. However, the necessary conditions governing engine performance and the relevant upper bound for efficiency are unknown for the general case of arbitrary spin magnitudes. By analyzing extreme case scenarios, we formulate heuristics to infer the necessary conditions for an engine with uncoupled as well as coupled spin model. These conditions lead us to a connection between performance of quantum heat engines and the notion of majorization. Furthermore, the study of complete Otto cycles inherent in the average cycle also yields interesting insights into the average performance.

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“…Encouragingly, the proof-of-principle Ge qubit devices have been experimentally demonstrated using Ge/SiGe planar heterostructures [ 15 , 30 ], Ge hut wires [ 31 ], and Ge/Si core/shell nanowires [ 32 ], respectively. Progresses in the optimization of Ge hole-based qubit devices based on these material platforms have excited important achievements in terms of large g-factors and spin-orbit interaction energies [ 33 ]. Each of these platforms offers specific advantages but also poses challenges, which have been comprehensively elaborated and reviewed in [ 33 ].…”

Section: Introductionmentioning

confidence: 99%

Germanium Quantum-Dot Array with Self-Aligned Electrodes for Quantum Electronic Devices

et al. 2021

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Semiconductor-based quantum registers require scalable quantum-dots (QDs) to be accurately located in close proximity to and independently addressable by external electrodes. Si-based QD qubits have been realized in various lithographically-defined Si/SiGe heterostructures and validated only for milli-Kelvin temperature operation. QD qubits have recently been explored in germanium (Ge) materials systems that are envisaged to operate at higher temperatures, relax lithographic-fabrication requirements, and scale up to large quantum systems. We report the unique scalability and tunability of Ge spherical-shaped QDs that are controllably located, closely coupled between each another, and self-aligned with control electrodes, using a coordinated combination of lithographic patterning and self-assembled growth. The core experimental design is based on the thermal oxidation of poly-SiGe spacer islands located at each sidewall corner or included-angle location of Si3N4/Si-ridges with specially designed fanout structures. Multiple Ge QDs with good tunability in QD sizes and self-aligned electrodes were controllably achieved. Spherical-shaped Ge QDs are closely coupled to each other via coupling barriers of Si3N4 spacer layers/c-Si that are electrically tunable via self-aligned poly-Si or polycide electrodes. Our ability to place size-tunable spherical Ge QDs at any desired location, therefore, offers a large parameter space within which to design novel quantum electronic devices.

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The germanium quantum information route

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Cited by 295 publications

References 252 publications

Crystalline materials for quantum computing: Semiconductor heterostructures and topological insulators exemplars

Crystalline materials for quantum computing: Semiconductor heterostructures and topological insulators exemplars

Quantum Heat Engines with Complex Working Media, Complete Otto Cycles and Heuristics

Germanium Quantum-Dot Array with Self-Aligned Electrodes for Quantum Electronic Devices

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