Tailoring quantum oscillations of a Bose-Einstein condensate of excitons as qubits
What plagues quantum upscaling? Most quantum computing devices are dependent on using complex physical phenomena that are either very short-lived (~10-12 seconds) and/or only survive at ultra-low temperatures (e.g., 10-3 ...
Experimental control of all these phenomena demand challenging experimental infrastructures such as ultra-cold atoms on optical lattices, atomic or ion traps, superconducting Josephson junctions and the use of a single semiconductor quantum dot. Most of these platforms are really difficult to scale up outside the boundaries of a sophisticated research laboratory. Decoherence is another major impediment in building a large quantum register of many qubits using these systems.
An alternative proposal based on experimental control of a Schrodinger's-cat-like macroscopic quantum state of many excitons
Instead of trying to entangle the quantum states of few "individual" qubits coherently in a brick-by-brick manner using bottom-up processes, we proposed a radically different top-down approach for building a large, N-qubit quantum register in our study published in the journal Materials Today Electronics.
This involves the generation and control of macroscopically large, Schrodinger's-cat like, two-level quantum coherent states of Bose-Einstein condensate (BEC) consisting of millions or more "identical" excitons (as bosons) in their quantum ground state using a zero-dimensional-two-dimensional (0D-2D) quantum-coupled heterostructure (Fig. 1).
Figure. 1. A schematic diagram of GaAs/AlAs/InAs/AlAs/GaAs double-barrier, 0D-2D heterostructure. Corresponding energy band-diagram is shown on the right. Oval shape shows the formation of 0D-2D indirect exciton. Credit: Materials Today Electronics (2023). DOI: 10.1016/j.mtelec.2023.100039
Figure 2. Schematics of spontaneous enhancement of electric polarization of 0D-2D excitons before and after excitonic dipoles collectively align along the vertical z direction during BEC. The small purple contours on the left represent the wave functions of individual excitons before the onset of BEC. The large wave function on the right roughly represents the macroscopic quantum state of excitonic BEC. Credit: Materials Today Electronics (2023). DOI: 10.1016/j.mtelec.2023.100039
Figure 3. Rabi oscillations of two-level "macroscopic" quantum states of coupled and uncoupled excitons at 10.5 K involving millions of quantum dots. Such Rabi oscillations were earlier reported only with structures having one single quantum dot only [3]. The observed Rabi oscillations measured with photocapacitance actually indicates "insignificant dephasing" even at this temperature and time scales probed in our steady state photocapacitance measurements. Credit: Materials Today Electronics (2023). DOI: 10.1016/j.mtelec.2023.100039
Figure 4. Diagrammatic representation of a quantum register based on excitonic BEC. Credit: Materials Today Electronics (2023). DOI: 10.1016/j.mtelec.2023.100039