Research And Design Of Cryogenic CMOS VCO For Classic-Quantum Interface

Quantum computing performs operations by using quantum properties,and it has a parallel computing capability that far exceeds that of classical electronic computers,in specific fields such as cryptography and chemical reaction calculations.In recent years,the field of quantum computers has developed rapidly.Quantum computer includes quantum chip and quantum interface.The hardware basis of quantum interface is the measurement and controller of qubits.There are surging demands for scaling of qubits in practical quantum algorithms,and coming with the need for larger-scale qubit measurement and controller system.The current quantum chip works in the extremely low temperature environment created by the dilution refrigerator,but the measurement and controller system is placed at the external room temperature,which is bulky,low in integration,poor in scalability,and complicated in connection,so room temperature measurement and controller system becomes a bottleneck for sacle expansion.Therefore,cryogenic CMOS measurement and controller chips for quantum interface,have become a research hotspot in recent years due to their high integration,low cost and digital compatibility.Firstly,thesis introduces cryogenic CMOS measurement and controller system for quantum interface,as well as its research status and development trend.Then thesis focuses on the cryogenic frequency source and voltage-controlled oscillator in the quantum measurement and controller system.Thesis summarizes the difficulties in designing a cryogenic CMOS oscillator in 4K low-temperature environment,and analyzes the reasons for the deterioration of phase noise in 4K.Then,the advantages and disadvantages of three representative cryogenic oscillators are analyzed in detail,on this basis,a feasible scheme of cryogenic voltage-controlled oscillator is proposed.Secondly,thesis designs a cryogenic CMOS voltage-controlled oscillator working at12.8-16.5GHz.In order to overcome the deterioration of flicker noise at low temperature,a transformer with an 8-shape head transformer is proposed.The 8-shape head transformer resonates with the common-mode capacitor,creating a double resonance point at the second harmonic,so that the oscillator has a broadband calibration-free 2^ndharmonic common-mode resonance.Even if the cryogenic environment causes the resonance frequency shift,effective harmonic alignment is also can be achieved to suppress the deterioration of flicker noise.In addition,thesis analyzes the shortcomings of a traditional unbalanced head transformers,which unbalanced magnetic field coupling leads to narrow-band flicker noise suppression.On the contrary,the proposed 8-shape head transformer is a balanced structure with balanced magnetic field coupling,which can achieve a wider bandwidth of flicker noise suppression.Finally,thesis shows the chip photo,the setup of the cryogenic test and the measured data results.The chip is taped out by 65nm CMOS process with a core area of 0.093mm².In 4.2K,the measured power consumption is only 1.1m W with a 0.63V low-voltage power supply;the measured output frequency range is 12.8-16.5GHz,and the relative bandwidth is 25.1%;the best measured Fo M is 202.3d Bc/Hz,which is best record.The measured phase noise in the full frequency band is not sensitive to temperature,and the flicker noise corner does not deteriorate at 4.2K,which shows that the proposed cryogenic CMOS voltage-controlled oscillator is effective.