STUDY ON COHERENT-ELECTRON-OSCILLATION DEVICES USING COUPLED-QUANTUM-STRUCTURES

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IN ORDER TO IMPLEMENT THE NEW OPTO-ELECTRONICS QUANTUM HARDWARES FOR INFORMATION PROCESSING, WE HAVE INVESTIGATED THE COHERENT-DYNAMICS OF THE QUANTUM (ATOM AND ELECTRON) WAVE IN THE SEMICONDUCTOR QUANTUM STRUCTURES AS WELL AS LASER-COOLED ATOMS AND THE BOSE-EINSTEIN CONDENSATES IN THE PRESENCE OF EXTERNAL CONTROL FIELDS SUCH AS LASER FIELD, ELECTRIC FIELD, AND MAGNETIC FIELD.THE MAIN RESULTS OBTAINED ARE AS FOLLOWS :(1) WE HAVE STUDIED THE ROTATIONAL MODE OF THE ELECTRONS IN THREE-COUPLED QUANTUM DOTS, WHICH ARE LOCATED AT THE APEXES OF AN EQUILATERAL TRIANGLE, UNDER THE INFLUENCE OF A ROTATIONAL ELECTRIC FIELD.TWO ROTATIONAL MODES ARE PREDICTED ; ONE IS THE COROTATIONAL ONE WHERE THE ELECTRONS ROTATE THE SAME DIRECTION AS THE ROTATING ELECTRIC FIELD AND THE OTHER IS THE COUNTER-ROTATIONAL ONE WHERE THE ELECTRONS ROTATE THE OPPOSITE DIRECTION TO THE ROTATING ELECTRIC FIELD.(2) DYNAMICAL CONTROL OF QUANTUM TUNNELING IN A COUPLED QUANTUM WELL HAS BEEN PREDICTED TO OCCUR WHEN LASER PULSES DRIVE SUBLEVEL TRANSITIONS IN ONE OF THE WELLS.IT WAS SHOWN FOR AN EXAMPLE THAT COMPLETE TUNNELING OSCILLATIONS CAN BE REALIZED, EVEN BETWEEN THE NONRESONANT STATES, BY MEANS OF A TRAIN OF SHORT PULSES WITH APPROPRIATE PULSE INTERVAL AND PULSE AREA.THIS PHENOMENON CAN BE UNDERSTOOD AS THE PHASE MATCHING IN TIME-DOMAIN.(3) WE HAVE INVESTIGATED ATOMIC POPULATION DYNAMICS OF TWO BOSE-EINSTEIN CONDENSATES THAT ARE IN DIFFERENT TRAPS OR IN THE SAME TRAP AND ARE OPTICALLY COUPLED THROUGH A COMMON EXCITED STATE BY RAMAN LASER PULSES.FOR LARGE INTERATOMIC INTERACTIONS, ALMOST ALL OF THE ATOMS THAT ARE INITIALLY IN ONE OF THE TRAPS (OR ONE OF THE INTERNAL STATES) ARE EITHER COMPLETELY TRANSFERRED INTO THE OTHER STATE OR STAY IN THE INITIALLY OCCUPIED STATE AFTER THE LASER PULSES.EVENTUALLY, THE ATOMS (POPULATIONS) ARE NEVER DISTRIBUTED TO BOTH CONDENSATE STATES AT THE SAME TIME.