Nanoscale broadband transmission lines for spin qubit control

The intense interest in spin-based quantum information processing has caused an increasing overlap between two traditionally distinct disciplines, such as magnetic resonance and nanotechnology. In this work we discuss rigourous design guidelines to integrate microwave circuits with charge-sensitive nanostructures, and describe how to simulate such structures accurately and efficiently. We present a new design for an on-chip, broadband, nanoscale microwave line that optimizes the magnetic field driving a spin qubit, while minimizing the disturbance on a nearby charge sensor. This new structure was successfully employed in a single-spin qubit experiment, and shows that the simulations accurately predict the magnetic field values even at frequencies as high as 30 GHz.Comment: 18 pages, 8 figures, 1 table, pdflate

An addressable quantum dot qubit with fault-tolerant control fidelity

Exciting progress towards spin-based quantum computing has recently been made with qubits realized using nitrogen-vacancy (N-V) centers in diamond and phosphorus atoms in silicon, including the demonstration of long coherence times made possible by the presence of spin-free isotopes of carbon and silicon. However, despite promising single-atom nanotechnologies, there remain substantial challenges in coupling such qubits and addressing them individually. Conversely, lithographically defined quantum dots have an exchange coupling that can be precisely engineered, but strong coupling to noise has severely limited their dephasing times and control fidelities. Here we combine the best aspects of both spin qubit schemes and demonstrate a gate-addressable quantum dot qubit in isotopically engineered silicon with a control fidelity of 99.6%, obtained via Clifford based randomized benchmarking and consistent with that required for fault-tolerant quantum computing. This qubit has orders of magnitude improved coherence times compared with other quantum dot qubits, with T_2* = 120 mus and T_2 = 28 ms. By gate-voltage tuning of the electron g*-factor, we can Stark shift the electron spin resonance (ESR) frequency by more than 3000 times the 2.4 kHz ESR linewidth, providing a direct path to large-scale arrays of addressable high-fidelity qubits that are compatible with existing manufacturing technologies

Qubits made by advanced semiconductor manufacturing

AbstractFull-scale quantum computers require the integration of millions of qubits, and the potential of using industrial semiconductor manufacturing to meet this need has driven the development of quantum computing in silicon quantum dots. However, fabrication has so far relied on electron-beam lithography and, with a few exceptions, conventional lift-off processes that suffer from low yield and poor uniformity. Here we report quantum dots that are hosted at a 28Si/28SiO2 interface and fabricated in a 300 mm semiconductor manufacturing facility using all-optical lithography and fully industrial processing. With this approach, we achieve nanoscale gate patterns with excellent yield. In the multi-electron regime, the quantum dots allow good tunnel barrier control—a crucial feature for fault-tolerant two-qubit gates. Single-spin qubit operation using magnetic resonance in the few-electron regime reveals relaxation times of over 1 s at 1 T and coherence times of over 3 ms.</jats:p

Noise analysis in super-regenerative receiver systems

The recent increase in the need for energy efficient wireless nodes have led to the study of various low power consumption receiver and transmitter architectures. The super-regenerative receiver architecture is one of the possible candidates for such a low power application. In this paper a detailed study on the noise analysis for such a kind of receiver is carried out. A closed form representation of the output signal to noise ratio for both narrow-band and wide-band communication is derived. The result indicates for a narrow-band communication the output signal to noise ratio cannot be better than a normal tuned amplifier. In the wide-band mode the SNR of super-regenerative receiver in linear regime is similar to a tuned amplifier. ©2008 IEEE

A 7.5mA 500 MHz UWB receiver based on super-regenerative principle

Low power impulse radio-ultra wide band(IR-UWB) receivers have potential application in the area of wireless sensor networks. In this paper the possibility of super-regenerative receivers for pulse detection is demonstrated. The super-regenerative receiver is implemented in a 0.18 μm CMOS process for a 500 MHz bandwidth (-3 dB) centered at 3.8 GHz. The receiver is operating at 1.5 V and consumes a peak current of 7.5 mA. The receiver shows a 16.5 mV amplitude difference between the presence and absence of a pulse at an average received power of -91.3 dlim at a pulse repetition rate of 1 MHz. © 2008 IEEE