Quantum entanglement formation by repeated spin blockade measurements in a spin field-effect transistor structure embedded with quantum dots

State tomography of a chain of qubits embedded in a spin field-effect transistor via repeated spin-blockade measurements on the edge qubit

“…1. 4,5 A series of quantum dots is embedded in the FET structure just above the channel. A single electron is confined in each quantum dot and quantum information is encoded on its spin states, ͉ ↑ ͘ and ͉ ↓ ͘.…”

“…We call it "spin-blockade measurement." 4,5 The feasibility of the present system is discussed in Ref. 5; ͑i͒ the selective access to each individual qubit via ESR becomes possible by slightly modifying the compound ratio x of the In 1−x Ga x As quantum dot, since the g factor of the electron in a dot is altered in this way 18 and the ESR absorption spectra of the electrons in different dots can be separated; ͑ii͒ the strength of the exchange interaction energy between qubits and the corresponding characteristic time scale are estimated, showing the feasibility; ͑iii͒ the modulation of the channel current by single electron charging in a quantum dot adjacent to the channel has been demonstrated in a trial structure with a single layer of quantum dot with unpolarized channel current.…”

“…1͒. 4,5 For quantum information processing, one should be able to perform initialization, quantum gate operations, and readout of the qubits. 6 In the proposed setup depicted in Fig.…”

Feasibility study of a semiconductor quantum bit structure based on a spin FET embedded with self-assembled InAs quantum dots

“…We proposed a method of constructing quantum bits made of stacked quantum dots buried adjacent to the channel of a spin field-effect transistor by spin blockade measurements of a single-dot spin state [1]. In this article, we show the feasibility study of the proposal [1] by experimentally verifying the single electron charging of a single dot above the 1D channel through channel conductance modulation. We will also investigate device design considerations in order to optimize the exchange interaction between the quantum bits.…”

A controlled-NOT gate in a chain of qubits embedded in a spin field-effect transistor and its process tomography

“…Initialization and entanglement generation of multiple qubits can be realized via repeated measurements only on the edge qubit. 5 The state tomography of qubits was discussed in Ref. 7.…”