約瑟夫森介面型人造原子和超導共振腔光場可相互耦合，形成電路量子電動力學（circuit QED）結構體系。由於circuit QED體系原子與光的交互作用可達強耦合，以及系統物理參數可快速調變，此體系可用於量子電動力學和量子場論在未開發領域的研究。circuit QED體系甚至適用於量子信息處理各個方面的應用開發，尤其是量子計算，因為它具有面對擴展工程複雜度時，可能所需的彈性。此計畫主旨是開發用於circuit QED架構中，操控超導電路系統量子狀態的實驗技術。我們規劃採用transmon型人造原子設計來實現超導量子位元和共振腔之間的強耦合，將特別關注量子位元狀態在時域中的操縱和量子位元間量子糾纏態的產生。為此，我們將以共振腔共振頻率附近的微波傳輸同相正交量測，實現量子位元狀態隨時間的可靠監測。我們也必須發展微波脈衝技術，用以任意操控量子位元在Bloch sphere上的位置。通過可靠的即時量子位元狀態監測，以及量子位元狀態任意操控，我們將使兩個量子位元間產生耦合，調製雙量子位元糾纏態，並檢試兩個量子位元的狀態相關性。兩個耦合的transmons，亦可形成耦合強度可調變的量子位元，我們會將其應用於相對論性量子電動力學研究。最後，我們計劃開發微波單光子源，應用於未來circuit QED實驗和量子信息處理。 ;Josephson-junction-based artificial atoms and superconducting cavities can couple to each other and form circuit quantum electrodynamics (QED) architecture, which is perfect for studying quantum electrodynamics and quantum field theory in new regime owing to strong coupling between atom and light and fast modulation of physical parameters are achievable. This architecture is even ideal for application developments in various aspects of quantum information processing, especially quantum computation, due to its potential flexibility for complexity of scaling-up engineering. This proposal is to develop experimental techniques for manipulating quantum states of superconducting circuit systems in circuit QED architecture. We plan to adapt transmon qubit design to achieve strong coupling between qubit and cavity. We will particularly focus on manipulation of qubit state in time domain and on creation of quantum entanglement between qubits. To do that, we will develop reliable qubit state measurement in real time based on homodyne detection of microwave transmission near resonance frequency of coupled cavity. We also have to develop necessary microwave pulsing techniques to fully manipulate single-qubit state on the entire Bloch sphere. With reliable real-time qubit state readout and full manipulation of qubit state, we plan to introduce coupling between two qubits to create entangled states and to test their correlation properties. Two coupled transmons can also form a tunable coupling qubit, which will be implemented to relativistic QED studies. Finally, we plan to generate microwave single-photon source for future circuit QED experiments and quantum information processing developments.
