Monolithic CMOS Qubit Circuits for Higher-Temperature Readout
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current silicon-based electron-spin and hole-spin coupled quantum-dot qubits operate effectively only at temperatures below 100 mK due to low confinement and coupling energies, limiting their integration and scalability in commercial CMOS technology.
Innovation Solution
The development of a monolithic qubit integrated circuit using minimum size undoped channel double-gate MOSFETs in a fully depleted silicon on insulator (FDSOI) process, featuring Si1-xGex/Si1-yGey heterojunctions for hole confinement, allows for higher temperature operation and integration of qubits with readout circuits on the same die.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If silicon-based electron-spin and hole-spin coupled quantum-dot qubits are used, then integration in commercial CMOS technology is enabled, but operation is restricted to temperatures below 100 mK due to low confinement and coupling energies
Solution Approach 1:
The patent changes the material composition parameter by introducing SiGe/Si heterostructures with specific germanium concentrations (x and y where 0 < x < y < 0.5) to increase confinement energy from tens of μeV to meV scale, enabling operation at temperatures above 100 mK while maintaining CMOS compatibility
Solution Approach 2:
The patent uses composite SiGe/Si heterostructure materials combining silicon and germanium in specific layers to create quantum wells and barriers with enhanced confinement properties, achieving higher operating temperatures while remaining compatible with standard CMOS fabrication processes
2Ease of manufacture
If qubit array chips are packaged separately with microwave control electronics on a separate die, then manufacturing is simplified, but readout fidelity and computing speed degrade due to atto-Farad capacitance driving 50Ω and 100× larger capacitance interconnect off-chip
Solution Approach 1:
The patent merges the qubit array chip with microwave control and readout electronics onto a single monolithic integrated circuit, eliminating off-chip interconnects and their associated capacitance issues, thereby preserving readout fidelity while enabling scalable quantum computing
3Productivity
If multi-chip approach is used, then high yield and high fr/fMAX transistors can be accommodated, but interconnect and fidelity challenges arise from driving large capacitance off-chip
Solution Approach 1:
The patent integrates qubits, control electronics, and readout circuits on a single monolithic chip, eliminating the need for complex off-chip interconnects and capacitance management while maintaining compatibility with high-yield standard CMOS manufacturing processes
4Ease of manufacture
If conventional quantum dot structures are used, then manufacturing is straightforward, but confinement and coupling energies remain in the tens of μeV range comparable to thermal noise at 100 mK
Solution Approach 1:
The patent employs SiGe/Si composite heterostructures with graded germanium composition to create quantum wells and barriers that provide meV-scale confinement energies, significantly exceeding thermal noise levels even at elevated temperatures, while remaining fabricable with standard CMOS techniques
Solution Approach 2:
The patent modifies the energy confinement parameter by adjusting germanium concentration gradients (0 < x < y < 0.5) in SiGe/Si heterostructures to optimize quantum well depth and barrier height, achieving confinement energies in the meV range suitable for operation above 100 mK
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables qubits with higher confinement and coupling energies, permitting operation above 1 K and facilitating large-scale monolithic quantum computing by improving readout fidelity and computing speed.
Implementation Method 1
Si1-xGex/Si1-yGey heterojunctions between the source and the channel and between the drain and the channel, whose role is to provide hole confinement in the undoped channel which acts as a 3D quantum dot
Implementation Method 2
a qubit realized as the minimum size (Lmin, Wmin) undoped channel double-gate electron- or hole-channel metal-oxide-semiconductor field-effect transistor (MOSFET)
Data Source
AI summary
Described is a monolithic integrated circuit for use in quantum computing based on single and multiple coupled quantum dot electron- and hole-spin qubits monolithically integrated with the mm-wave spin manipulation and readout circuitry in commercial complementary metal-oxide-semiconductor (CMOS) technology. The integrated circuit includes a plurality of n-channel or p-channel metal-oxide-semiconductor field-effect transistor (MOSFET) cascodes each including a single-spin qubit or two coupled quantum dot qubits formed in an undoped semiconductor film adjacent at least one top gate. There is also a back gate formed in a silicon substrate adjacent a buried oxide layer or the at least one top gate, where the back gate controls the electron or hole entanglement and exchange interaction between the two coupled quantum dot qubits. The monolithic integrated circuits described may be used for monolithically integrated semiconductor quantum processors for quantum information processing.