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Project

A cryogenic ADC for quantum computering in 28nm Technology

  Normally, a quantum computer consists of quantum processor and classical controller. The core of a quantum processor is an array of quantum bits (qubits) which are the basic logic unit of quantum computation. Due to the coherence of quantum states, only at temperatures near absolute zero(tens of mK) can accuracy of quantum computing be ensured. Today, the control circuit and system of qubits for reading out work at room temperature, while qubits operate at several tens of milli-Kelvin. Nevertheless, controller is implemented with room-temperature becomes increasingly challenging and less cost-effective as the number of qubits grows toward the thousands and millions, as required by practical quantum algorithms. To ensure compactness, and eventually scalability, it has been proposed that controllers are designed to operate at several Kelvin and to locate as close as possible to the source of signal, so as to reduce the length of control cables, which enable virtually zero resistance and low thermal conductivity. A generic classical control system is is surprisingly similar to a radio-frequency transceiver, given the similarity, in principle, of its functions. The task of controller includes amplifying weak signal (hundreds of dBm) and converting it into digital code with high fidelity of amplitude and phase better than 1 LSB and 1 degree, respectively. Signal indicating state of a qubit requires a fidelity of 99.99-99.999%. In order not to disturb the quantum state of the qubit, the controller must generate accurate and extremely low-noise signals. Above all, cryogenic working environment for quantum computing has a high requirement against performance and stability of control system. For control system with a large number of analog channels, cryogenic ADC is one crucial component as it simplify the cryostat design, eliminates the need of analog buffers, and allows for a higher channel density.

Date:2 Dec 2019 →  2 Dec 2023
Keywords:cryogenic, ADC
Disciplines:Analogue, RF and mixed signal integrated circuits
Project type:PhD project