Quantum dots proved to be well controlled quantum mechanical systems. In analogy to real atoms and molecules, single quantum dots and double quantum dots are termed artificial atoms and artificial molecules, respectively. In microwave spectroscopy, continuous microwave radiation is applied to quantum dots. Photon-assisted tunneling PAT through the ground state and excited states is observed in single quantum dots.
In a double quantum dot, the molecular states can be coherently superimposed by microwave photons, inducing the Rabi oscillations and a net direct tunnel current which is experimentally measurable. A qubit is formed in a double quantum dot.
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Two new microwave spectroscopy techniques are developed in this thesis to explore the dynamics of PAT SET in quantum dots. Both techniques are called heterodyne detection of photon-induced tunnel current photocurrent.
In one method, two coherent continuous microwave sources with a slight frequency offset are combined to generate a flux of microwave photons. The photon intensity varies in time at the offset frequency. The induced alternating photocurrent at the offset frequency is detected by a lock-in amplifier. The in-phase component of the photocurrent reflects the tunneling strength, and the out-of-phase component reveals the dynamics of electron tunneling.
In the other method, two coherent pulsed, i. Explore further. To exploit their power, it is necessary to perform interqubit operations and generate entangled states. Spin qubits are a promising candidate for implementing a quantum processor because of their potential for scalability and miniaturization. However, their weak interactions with the environment, which lead to their long coherence times, make interqubit operations challenging.
We performed a controlled two-qubit operation between singlet-triplet qubits using a dynamically decoupled sequence that maintains the two-qubit coupling while decoupling each qubit from its fluctuating environment.
Quantum control of delocalized quantum bits in semiconductors – QCONTROL
Using state tomography, we measured the full density matrix of the system and determined the concurrence and the fidelity of the generated state, providing proof of entanglement. Journal information: Science. More from Other Physics Topics. Please sign in to add a comment.
Coherent manipulation of semiconductor quantum bits with terahertz radiation
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