Fabrication And Studying The Performance Of Josephson Parameter Amplifier And Multi-bit Quantum Chip For Superconducting Quantum Computing

In this thesis I first introduced the development stages of the Quantum computing.They include theoretical research,accelerating effect algorithm proposed and in various types of hardware platform to develop quantum computing.At present,one of the most important scheme for developing quantum computers is to use superconducting Josephson junction qubits as the basic building blocks.Nearly five to ten years,the superconducting quantum bits decoherence has made great progress.International and domestic began to study the quantum chip which contains a number of superconducting quantum bits.In this aspect,one is to prepare a multi-bit chip with good performance.The other is to prepare a Josephson parametric amplifier to amplify the qubit signal over a wide bandwidth to achieve simultaneous quantitation of multiple quantum bits Single shot non-destructive measurement.This paper introduces the research work done in these two fields during the Ph.D.Firstly,the research background is introduced.The basic principle and development process of quantum computation and quantum information are briefly introduced.The structure and theory of superconducting qubits and Josephson parametric amplifiers are emphatically introduced.And introduced the actual research progress.The essay proposes to solve the problem that in a wide bandwidth range,amplifying the noise level close to the quantum limit on the signal of energy scale in a single microwave photon.I have studied the subject,started a large number of systematic work,the content is summarized as participating in the group with a number of microwave cable measurement system;preparation of Josephson parametric amplifier,multi-bit quantum chips;with a number of research units,the preparation The performance of the device was studied.The broadband Josephson parametric amplifier and the superconducting quantum chip were characterized on the self-built system.The details of the work include the design of a photolithographic mask,the design of the test structure,the preparation and characterization of the test structure,and the repeated exploration of the various process parameters to form a complete micro-nano for the preparation of a Josephson parametric amplifier Processing technology.One of the process features is the use of wet etching of Al thin films.Relative to the dry etching of Al thin film,wet etching using a small water bath instrument,easy to operate,the cost is relatively low,to avoid the use of toxic gas etching.Narrowband Josephson parametric amplifiers were successfully fabricated through this process.The narrowband Josephson parametric ampli fi er with a gain above 14 dB has a bandwidth of around 35 MHz.The noise level is about 400 mK,close to the quantum limit level.The narrowband amplifier is used for single superconducting quantum bit quantum state readout,which obviously improves the signal-to-noise ratio of the readout signal.Based on the process of preparing the narrowband parametric amplifier,a batch of wide-band Josephson parametric amplifiers was prepared on a two-inch Si substrate using an EBPG 100 KeV electron beam lithography machine.The prepared wideband Josephson parametric amplifier 14 d B The above gain bandwidth reaches about 200 MHz.A number of research groups conducted a quantum experiment with a prepared wideband parametric amplifier to realize simultaneous single-shot non-destructive readout of quantum states of multiple quantum bits.And significantly improves the signal-to-noise ratio of the readout signal.The experiment on multi-bit preparation is as follows.A set of process for preparing Xmon-type quantum chips on alumina substrate was explored.Multi-chip 5-bit quantum chips and 10-bit quantum chips were prepared.The Cross Over of the Al / SiO2 / Al structure is fabricated on a microwave control line of a multibit device,forming an effective connected ground plane,significantly reducing crosstalk between different bits.With the Cross Over of this structure added,the crosstalk between bitcontrolled drive lines is significantly reduced.Preliminary characterization results show that the energy relaxation time of the prepared five-bit chip is on the order of 10 ?s.Through a large amount of work in the system,the thesis has completed the preparation of superconducting quantum chips and Josephson parametric amplifier,and studied the characterization.It has laid a solid foundation for the domestic cooperative research group and our superconducting multi-quantum bit research system.