Semiconductor quantum bits: Structures and principles

Tetsuo Kodera

Christian Schimpf, Marcus Reindl, Daniel Huber +6 more

Semiconductor quantum dots are capable of emitting polarization entangled photon pairs with ultralow multipair emission probability even at maximum brightness. Using a quantum dot source with a fidelity as high as 0.987(8), we implement here quantum key distribution with an average quantum bit error rate as low as 1.9% over a time span of 13 hours. For a proof of principle, the key generation is performed with the BBM92 protocol between two buildings, connected by a 350-m-long fiber, resulting in an average raw (secure) key rate of 135 bits/s (86 bits/s) for a pumping rate of 80 MHz, without resorting to time- or frequency-filtering techniques. Our work demonstrates the viability of quantum dots as light sources for entanglement-based quantum key distribution and quantum networks. By increasing the excitation rate and embedding the dots in state-of-the-art photonic structures, key generation rates in the gigabits per second range are in principle at reach.

Yerzhan Mustafa, Selçuk Köse

Interface circuits are the key components that enable the hybrid integration of superconductor and semiconductor digital electronics. The design requirements of superconductor-semiconductor interface circuits vary depending on the application, such as high-performance classical computing, superconducting quantum computing, and digital signal processing. In this survey, various interface circuits are categorized based on the working principle and structure. The superconducting output drivers are explored, which are capable of converting and amplifying, e.g., single flux quantum (SFQ) voltage pulses, to voltage levels that semiconductor circuits can process. Several trade-offs between circuit- and system-level design parameters are examined. Accordingly, parameters such as the data rate, output voltage, power dissipation, layout area, thermal/heat load of cryogenic cables, and bit-error rate are considered.

Anasua Chatterjee, Paul Stevenson, Silvano De Franceschi +3 more

Yuriy Makhlin, Gerd Schön, Alexander Shnirman

C. C. Kuo, Connie J. Chang-Hasnain, Jungho Kim +1 more

A variable semiconductor all-optical buffer is proposed. The buffer uses electromagnetically-induced transparency in quantum dots. With resonator structures, the performance can be further improved. A device storing 168 bits in a 10 Gb/s system can be obtained at room temperature.