Silicon offers an attractive material platform for hardware realization of quantum computing. In this study, a microscopic stochastic simulation method is developed to model the effect of random interface charge traps in silicon metal-oxide-semiconductor (MOS) quantum gates. The statistical results show that by using a fast two-qubit gate in isotopically purified silicon, the two-qubit silicon-based quantum gates have the fidelity >98% with a probability of 75% for the state-of-the-art MOS interface quality. By using a composite gate pulse, the fidelity can be further improved to >99.5% with the 75% probability. The variations between the quantum gate devices, however, are largely due to the small number of traps per device. The results highlight the importance of variability consideration due to random charge traps and potential to improve fidelity in silicon-based quantum computing.
The prospect of building a quantum information processor underlies many recent advances ion trap fabrication techniques. Potentially, a quantum computer could be constructed from a large array of interconnected ion traps. We report on a micrometer-scale ion trap, fabricated from bulk silicon using micro-electromechanical systems (MEMS) techniques. The trap geometry is relatively simple in that the electrodes lie in a single plane beneath the ions. In such a trap we confine laser-cooled 24Mg+ ions approximately 40 microns above the surface. The fabrication technique and planar electrode geometr…
Trapped ions are pre-eminent candidates for building quantum information processors and quantum simulators. They have been used to demonstrate quantum gates and algorithms, quantum error correction, and basic quantum simulations. However, to realise the full potential of such systems and make scalable trapped-ion quantum computing a reality, there exist a number of practical problems which must be solved. These include tackling the observed high ion-heating rates and creating scalable trap structures which can be simply and reliably produced. Here, we report on cryogenically operated silicon i…
In this paper we present the design, modeling, and experimental testing of surface electrode ion traps fabricated in a heterostructure configuration comprising a silicon substrate, silicon dioxide insulators, and aluminum electrodes. This linear trap has a geometry with symmetric RF leads, two interior DC electrodes, and 40 individual lateral DC electrodes. Plasma enhanced chemical vapor deposition (PECVD) was used to grow silicon dioxide pillars to electrically separate overhung aluminum electrodes from an aluminum ground plane. In addition to fabrication, we report techniques for modeling th…
Pulsed electrically-detected magnetic resonance of phosphorous (31P) in bulk crystalline silicon at very high magnetic fields (B > 8.5 T) and low temperatures (T = 2.8 K) is presented. We find that the spin-dependent capture and reemission of highly polarized (>95%) conduction electrons by equally highly polarized 31P donor electrons introduces less decoherence than other mechanisms for spin-to-charge conversion. This allows the electrical detection of spin coherence times in excess of 100 microseconds: 50 times longer than the previous maximum for electrically-detected spin readout experiment…
A Platform for Evanescently Trapping Rb-87 Using Silicon Nitride Strip Waveguides Buried in Silica
University of Bristol（布里斯托大学）；Quantum Engineering Technology Labs, H.H. Wills Physics Laboratory and School of Electrical, Electronic, & Mechanical Engineering, University of Bristol（布里斯托大学量子工程技术实验室、H.H. 威尔斯物理实验室和电气、电子与机械工程学院）；Quantum Engineering Centre for Doctoral Training, University of Bristol（布里斯托大学量子工程博士培训中心）
We study a nanofabricated silicon rod levitated in an optical trap. By manipulating the polarization of the light we gain full control over the ro-translational dynamics of the rod. We are able to trap both its centre-of-mass and align it along the linear polarization of the laser field. The rod can be set into rotation at a tuned frequency by exploiting the radiation pressure exerted by elliptically polarized light. The rotational motion of the rod dynamically modifies the optical potential, which allows tuning of the rotational frequency over hundreds of Kilohertz. This ability to trap and c…
The development of the first generation of commercial quantum computers is based on superconductive qubits and trapped ions respectively. Other technologies such as semiconductor quantum dots, neutral ions and photons could in principle provide an alternative to achieve comparable results in the medium term. It is relevant to evaluate if one or more of them is potentially more effective to address scalability to millions of qubits in the long term, in view of creating a universal quantum computer. We review an all-electrical silicon spin qubit, that is the double quantum dot hybrid qubit, a qu…
We propose a quantum computer architecture involving substitutional donors in photonic-crystal silicon cavities and the optical initialization, manipulation, and detection processes already demonstrated in ion traps and other atomic systems. Our scheme considerably simplifies the implementation of the building blocks for the successful operation of silicon-based solid-state quantum computers, including positioning of the donors, realization of one- and two-qubit gates, initialization and readout of the qubits. Detailed consideration of the processes involved, using state-of-the-art values for …
We trap individual $^{171}$Yb$^+$ ions in a surface trap microfabricated on a silicon substrate, and demonstrate a complete set of high fidelity single qubit operations for the hyperfine qubit. Trapping times exceeding 20 minutes without laser cooling, and heating rates as low as 0.8(0.1) quanta/ms indicate stable trapping conditions in these microtraps. A coherence time of more than one second, high fidelity qubit state detection and single qubit rotations are demonstrated.
Quantum-mechanical principles can be used to process information (QIP). In one approach, linear arrays of trapped, laser cooled ion qubits (two-level quantum systems) are confined in segmented multi-zone electrode structures. The ion trap approach to QIP requires trapping and control of numerous ions in electrode structures with many trapping zones. I investigated microfabrication of structures to trap, transport and couple large numbers of ions. Using 24Mg+ I demonstrated loading and transport between zones in microtraps made of boron doped silicon. This thesis describes the fundamentals of i…
Quantum computers have the potential to efficiently solve problems in logistics, drug and material design, finance, and cybersecurity. However, millions of qubits will be necessary for correcting inevitable errors in quantum operations. In this scenario, electron spins in gate-defined silicon quantum dots are strong contenders for encoding qubits, leveraging the microelectronics industry know-how for fabricating densely populated chips with nanoscale electrodes. The sophisticated material combinations used in commercially manufactured transistors, however, will have a very different impact on …
We demonstrate a hybrid device architecture where the charge states in a double quantum dot (DQD) formed in a Si/SiGe heterostructure are read out using an on-chip superconducting microwave cavity. A quality factor Q = 5,400 is achieved by selectively etching away regions of the quantum well and by reducing photon losses through low-pass filtering of the gate bias lines. Homodyne measurements of the cavity transmission reveal DQD charge stability diagrams and a charge-cavity coupling rate g_c/2pi = 23 MHz. These measurements indicate that electrons trapped in a Si DQD can be effectively couple…
Integrated technologies greatly enhance the prospects for practical quantum information processing and sensing devices based on trapped ions. High-speed and high-fidelity ion state readout is critical for any such application. Integrated detectors offer significant advantages for system portability and can also greatly facilitate parallel operations if a separate detector can be incorporated at each ion-trapping location. Here we demonstrate ion quantum state detection at room temperature utilizing single-photon avalanche diodes (SPADs) integrated directly into the substrate of silicon ion tra…
