What Does an Observed Atom Reveal to Its Observer?
Abstract
The acts of measurement, even unless intervening with the quantum object, impede the object's' evolution. This "quantum Zeno" effect has been contemplated for decades. An experimental demonstration had been attempted that applied a series of light pulses during the microwave-induced evolution of an ensemble of trapped ions, followed by measurement of the ensemble's state. The results completely agreed with quantum- mechanical predictions. However, the impediment of the quantum evolution by measurement cannot, in principle, be verified on an ensemble, since such an experiment yields, as the result, an expectation value, not an eigenvalue, and the micro-state of the system is not revealed by the measurement. Moreover, each radiative intervention requires subsequent detection of the emerging state in order to qualify as a measurement. A recent experiment used a single quantum system and has included repeatedly probing the state of the system-not just pulsed irradiation-alternating with the laser-driven evolution. Here, each measurement signals the micro-state of the system. The statistics of correlated results reveals the inhibiting effect of reiterated measurements on the microscopic system. The coherent laser excitation of the ion amounts to the implementation of the Hadamard transformation ("one-qubit quantum logic gate"), on an electronic resonance, important for application in quantum information processing by individually addressable atoms. Also, an ion has been coherently driven on the ground-state hyperfine transition by a microwave. In this system, which lacks intrinsic relaxation, again the impediment of the ion's evolution by repeated measurements was demonstrated.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jan 01, 2002
- Accession Number
- ADP015760
Entities
People
- C. Balzer
- P. E. Toschek
Organizations
- University of Hamburg