Tailoring Quantum Oscillations of Excitonic Schrodinger’s Cats as Qubits

We report [https://arxiv.org/abs/2107.13518] experimental detection and control of Schrodinger’s Cat like macroscopically large, quantum coherent state of a two-component Bose-Einstein condensate of spatially indirect electron-hole pairs or excitons. These excitons are artificial atom like quasi particles within solids which can be generated with optical and/or electrical excitations. As a result, achieving BEC within an optoelectronic device can provide access to millions of excitons as qubits to allow efficient, fault-tolerant quantum computation. In this work, phase coherent periodic oscillations in photo generated capacitance as a function of applied voltage bias and light intensity over a macroscopically large area are measured. Periodic presence and absence of splitting of excitonic peaks in the optical spectra based on photocapacitance point towards tunneling induced variations in capacitive coupling between quantum well and quantum dots. Observation of negative ‘quantum capacitance’ due to screening of charge carriers by the quantum well indicate Coulomb correlations of interacting excitons in the plane of the sample. Coherent resonant tunneling in this well-dot heterostructure restricts the available momentum space of the charge carriers within this quantum well. Consequently, the average electric polarization vector of the associated indirect excitons collectively orients along the direction of applied bias and these excitons undergo Bose-Einstein condensation below ~100 K. Generation of interference beats in photocapacitance oscillation even with incoherent white light further confirm the presence of stable, long range spatial correlation among these indirect excitons. Moreover, some of these photo generated excitons can be addressed independently of others using applied bias over a localized region. In addition, collective Rabi oscillations of these macroscopically large, ‘multipartite’, two-level, coupled and uncoupled quantum states of excitonic condensate as qubits are also observed. Therefore, our study not only brings the physics and technology of Bose-Einstein condensation within the reaches of semiconductor chips, but also opens up experimental investigations of the fundamentals of quantum physics using similar techniques. It is also obvious that most of the DiVincenzo’s criteria for quantum computation are also fulfilled in this system in principle. <br/> Operational temperature of such excitonic BEC can be raised further using similar 0D-2D heterostructure having more densely packed, ordered array of QDs in the x-y plane and/or using materials having larger excitonic binding energies. However, fabrications of single crystals of 0D-2D heterostructures using 2D materials (e.g. transition metal di-chalcogenides, oxides, perovskites etc.) having higher excitonic binding energies are still an open challenge for semiconductor optoelectronics. Even now these 0D-2D heterostructures can be scaled up for mass production of miniaturized, portable quantum optoelectronics devices using the existing III-V and/or Nitride based semiconductor fabrication technologies. Such feasibilities of fabricating quantum devices, however, certainly difficult to implement for most other current approaches being developed for quantum computation outside the boundaries of a sophisticated research laboratory. It can bring in a paradigm shift in optoelectronics for faster and wider adaptation of quantum technologies in terms of miniaturization and portability.