Today on the archive
Thu Aug 3 08:45:52 BST 2006
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- Title: Relativistic ionization-rescattering with tailored laser pulses
- Authors: Michael Klaiber, Karen Z. Hatsagortsyan, Christoph H. Keitel
- Abstract: The interaction of relativistically strong tailored laser pulses with an atomic system is considered. Due to a special tailoring of the laser pulse, the suppression of the relativistic drift of the ionized electron and a dramatic enhancement of the rescattering probability is shown to be achievable. The high harmonic generation rate in the relativistic regime is calculated and shown to be increased by several orders of magnitude compared to the case of conventional laser pulses. The energies of the revisiting electron at the atomic core can approach the MeV domain, thus rendering hard x-ray harmonics and nuclear reactions with single atoms feasible.
- Comment: The authors consider using specially tailored attosecond pulse trains (APT) to enhance high harmonic generation by increasing the rescattering probability of the excited electron. Normally as the laser pulse intensity is increased there is an increased force on the excited electron which causes drift that reduces the probability of the electron returning to the ioninc core and rescattering. Replacing the sinusoidal force on the electron with a series of short pulses means that the electron experiences the force from the laser only when it would be most beneficial for high harmonic generation. This seems to be the kicked quantum harmonic oscillator problem...
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- Title: Catalytic quantum error correction
- Authors: Todd Brun, Igor Devetak, Min-Hsiu Hsieh
- Abstract: We develop the theory of entanglement-assisted quantum error correcting (EAQEC) codes, a generalization of the stabilizer formalism to the setting in which the sender and receiver have access to pre-shared entanglement. Conventional stabilizer codes are equivalent to dual-containing symplectic codes. In contrast, EAQEC codes do not require the dual-containing condition, which greatly simplifies their construction. We show how any quaternary classical code can be made into a EAQEC code. In particular, efficient modern codes, like LDPC codes, which attain the Shannon capacity, can be made into EAQEC codes attaining the hashing bound. In a quantum computation setting, EAQEC codes give rise to catalytic quantum codes which maintain a region of inherited noiseless qubits. We also give an alternative construction of EAQEC codes by making classical entanglement assisted codes coherent.
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- Original title: Ultrafast coherent coupling of atomic hyperfine and photon frequency qubits
- New title: Ultrafast Coherent Excitation of a Trapped Ion Qubit for Fast Gates and Photon Frequency Qubits
- This is now published as [Phys. Rev. Lett. 97, 040505 (2006)]
[physics]
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