Quantum channel

Quantum Channel, Boundary Control, and State-Transfer Fidelity We consider a chain of + 2 spin- particles with XX interactions between nearest neighbors. The Hamiltonian is given by... 

Alice and Bob communicate via a quantum channel such as an optical fiber wire. 

The NIST system transmitted a stream of individual photons to create an encryption key (used to encrypt messages ) at the rate of 1 Million bits per second. A very impressive speed but this transmission was between two NIST buildings that are 730 meters apart. One of the issues is how to built repeaters which can allow long quantum channels. A 67 kilometers quantum transmission achieved in 2001 at the University of Geneva may be the longest possible distance with current technology. 

At present, advances in nanotechnology allow to create semiconductor nanostructures in which linear dimensions of the conductive channel in the direction of propagation of the electron wave are smaller than the mean free path of the electron. In such a channel particles move in a ballistic regime that allows to study experimentally the effects of ballistic transport in such structures, in particular, various electron interference effects [1]. A large number of theoretical works were devoted to the investigation of electron quantum ballistic transport in ID and 2D nanostructures whose common feature is the presence in quantum channels of regions of a sharp (nonadiabatic) variation either of the channel s geometry or a potential relief in it [2-4]. 

Because of nanoscale cross-section in carbon nanotubes, electrons spread only along the tube s axis and electron transfer includes quantum effects. As a result, carbon nanotubes are commonly referred to as one-dimensional conductors. The maximum electrical transmission of a SWNT is 2Gg, where G = 2e /h is the transmission of a single ballistic quantum channel. 

If the collision flux is prepared in a single quantum channel (sm), the collision wavefunction has the form... 

Quantum key distribution protocols establish secret keys via insecure quantum and/or classical channels. Existing quantum key distribution algorithms generally use two communication channels between Alice and Bob a quantum channel which transmits qubits and a classical channel for classical binary information. The classical channel is used to communicate measurement strategy, or the basis for measurement, and to check for eavesdropping. 

The algorithm uses a quantum channel and a classical channel, but unlike ah previous quantum key distribution algorithms, the classical channel is not authenticated. Authentication and security checking are done at the same time, after the algorithm, with the help of two public keys. 

As shown in this paper, quantum authentication can be done with the help of a variation of protected public keys. This might not be the only solution. It is an open problem what other structures can support authentication of quantum channels. 

For a single quantum channel where the contact diameter is comparable to, or less than, the Fermi wavelength, Iq is given by... 

Here h(x) is the Heaviside step function with h(x > 0) = 1 and h(x > 0) = 0 (not to be confused with Planck s constant). The limit a(J.. . ) indicates that the sunnnation is restricted to channel potentials witir a given set of good quantum numbers (J.. . ). 

Quack M and Suhm M A 1991 Potential energy surfaces, quasiadiabatic channels, rovibrational spectra, and intramolecular dynamics of (HF)2 and its isotopomers from quantum Monte Carlo calculations J. Chem. Phys. 95 28-59... 

Pogrebnya S K, Echave J and Clary D C 1997 Quantum theory of four-atom reactions using arrangement channel hyperspherical coordinates Formulation and application to OH + Hg < HgO + H J. Chem. Phys. 

Non-Radiative Decay Channels - 1064 nm Excitation. We turn now to a comparison of the observed fluorescence photon yield defined by Equation 1 and the expected fluorescence quantum yield of the 4550 cm 1 state which indicates that several non-radiative decay channels may be open following 1064 nm excitation of PuF6(g) The following relationship between... 

Figure 1.33 The underlying principle of the Redfield technique. Complex Fourier transformation and single-channel detection gives spectrum (a), which contains both positive and negative frequencies. These are shown separately in (b), corresponding to the positive and negative single-quantum coherences. The overlap disappears when the receiver rotates at a frequency that corresponds to half the sweep width (SW) in the rotating frame, as shown in (c). After a real Fourier transformation (involving folding about n = 0), the spectrum (d) obtained contains only the positive frequencies.

The problem of controlling the outcome of photodissociation processes has been considered by many authors [63, 79-87]. The basic theory is derived in detail in Appendix B. Our set objective in this application is to maximize the flux of dissociation products in a chosen exit channel or final quantum state. The theory differs from that set out in Appendix A in that the final state is a continuum or dissociative state and that there is a continuous range of possible energies (i.e., quantum states) available to the system. The equations derived for this case are... 

Figure 17. Internal energy distributions of HCO from photodissociation of CH2O at 2549 cm (upper panel) and 2627 cm (lower panel) above the threshold for the H + HCO channel. The HCO vibrational thresholds are labeled with their quantum numbers, and combs label the stack thresholds. The open circles show predictions of the SSE/PST model. The upper panel is indicative of an So dominant pathway. In the lower panel, T is dominant, but So structure can still be observed. Reprinted with permission from [51]. Copyright 2000, American Institute of Physics.

---