This paper discloses a mixed-signal control unit of a fully integrated semiconductor quantum processor SoC realized in a 22nm FD-SOI technology. Independent high-resolution DACs that set the amplitude and pulse-width of the control signals were integrated for each qubit, enabling both a programmable semiconductor qubit operation and a per-qubit individual calibration that compensates for the process variability. The lower deco-herence time of the semiconductor charge-qubits as compared to their spin-qubit counterparts was mitigated by using a high frequency of control unit operation. This is facilitated by the co-integration on the same die of the semiconductor quantum structures together with their corresponding classic control circuitry. The main challenge of achieving deep cryogenic operation for the mixed-signal classic control circuit was surpassed by using programmable local heating DACs that slightly boost the local temperature of the control blocks above the average temperature of the die, which needs to be maintained around 4 K to enable a reliable quantum operation. A staged multi-phase operation was adopted for the digital core in order to minimize the quantum decoherence originated in digital noise injection. The high-frequency clock tree and divider allows the generation of sub-20 ps fast edge control pulses with programmable widths down to 166 ps. This offers a wide quantum computation window when compared with the 1µs decoherence time of the charge-qubit structures.

The fundamental properties of two electrostatically interacting single-electron lines (SEL) are determined from a minimalistic tight-binding model. The lines are represented by a chain of coupled quantum wells that can be implemented in a mainstream nanoscale CMOS process technology and tuned electrostatically by DC or AC voltage biases. The obtained results show an essential qualitative difference with two capacitively coupled classical electrical lines. The derived equations and their solutions prove that the two coupled SET lines can create an entanglement between electrons. The correlation function characterizing the correlation/anticorrelation in electron position is introduced both in quantum and classical descriptions of capacitively coupled SELs. The quantum measurement conducted on quantum and classical SELs is described. The difference in quantum and classical ground states can be used as the probe determining the ‘quantumness’ of the SEL system. The results indicate a possibility of constructing electrostatic (non-spin) coupled qubits that could be used as a building block in a CMOS quantum computer.

Analytical solutions for a tight-binding model are presented for position-based charge qubits and N-interacting qubits realized by quasi-one-dimensional network of coupled quantum dots (QD) expressed by connected or disconnected graphs of any topology in two and three dimensions where one electron is present at each separated graph. Electron(s) quantum dynamical state is described under various electromagnetic circumstances with omission spin degree-of-freedom. The action of Hadamard and phase-rotating gates is given by analytical formulas derived and formulated for any case of a physical field evolution preserving the occupancy of a two-energetic-level system. The interface between a superconducting Josephson junction and semiconductor position-based qubit implemented in coupled semiconductor QDs is described, which can be the base for electrostatic interface between superconducting and semiconductor quantum computer. Modification of Andreev Bound State in Josephson junction by the presence of semiconductor qubit in its proximity and electrostatic interaction with superconducting qubit is supported by the minimalistic tight-binding model that also can indicate topological phase transition. The obtained results can be generalized for a case of electrostatic interaction of the semiconductor qubit with the different types of Josephson junctions. The operation of phase rotating gate implemented in semiconductor position-based qubit with use of electrical and magnetic field is presented with use of analytical approach.

Purpose: The lack of reliable and scalable superconducting random access memory (RAM) cells is the main obstacle for full implementation of superconducting rapid single flux quantum(RSFQ) computers. This work points the methodology and the structures that shall be used in future implementation of RSFQ RAM. Design/methodology/approach: A new design for RAM using two ferromagnetic strips in proximity to the superconductor in a RSFQ computer is presented (1). The concept of using a RAM RSFQ cell as a tuneable superconducting qubit is also explored. Findings: Two basic architectures for superconducting RAM cells were developed with integration schemes in two dimensions. Research limitations/implications: The proposed RAM cells as depicted in Figures 7 and 16 offer smaller size and greater 3 scalability in comparison to other suggested schemes (4), (3), (2), (5). Practical implications: Currently, the main obstacle in implementation of RSQF computer is lack of reliable RAM cell. RSQF computer shall have potential to take a large fraction of classical supercomputers, as it consumes much less power. Social implications: Computation power shall be cheaper when one uses RSQF computers for big data and computational centres. It is a matter of some time. Originality/value: The publication presents the new design of superconducting RAM cell for use in RSQF computer. The numerical relaxation method is used to solve biharmonic Ginzburg–Landau equation. The analytic approach as a solution of a specified problem is given.