Coherence and Quantum Optics VIII pp 631-632 | Cite as

# Quantum solitons as possible qubits

Conference paper

## Abstract

In a recent article [1] Izo Abram, of the Centre National d’Etudes des Télécommunlcations (CNET), Bagneux, France suggested that Inline 1\( \geqslant \frac{{p - 1}}{m} \) where the oscillatory phase exp iФ(x, t) is determined by where ξ, η θ

*quantum solitons*in optical fibres could both be ‘squeezed’ below the short noise level, thus*reducing*quantum noise, and that they could be used as natural ‘qubits’ for quantum information, quantum computing, logic gates, etc. The point here is that*multi*-quantum solitons are more easily realised experimentally (in an optical fibre) than are the current realisations of qubits using spin-1/2 systems or as in [2] using 2-level atoms and/or single photons in the context of cavity q.e.d, The ‘quantum soliton’ as described by Abram [1] is the 1-soliton solution of the well known classical one-dimensional attractive Nonlinear Schrödinger (NLS) equation which solution can be put in the form [3]$$ \langle {(\Delta \hat{A})^2}\rangle \langle {(\Delta \hat{B})^2}\rangle \geqslant \frac{1}{4}|\langle \psi |[\hat{A}\hat{B}] - |\psi \rangle {|^2} $$

(1)

$$ P\{ \phi (t) = \psi (t)\} = 1 $$

(1.2)

_{0}are all real valued parameters: c〈0 is the coupling constant of the NLS equation. Quantum features on this classical soliton are then introduced ([1, 4, 5] and see [6]) by imposing momentum-position uncertainly or number phase uncertainly, the latter in particular satisfying Δ*n*Δφ≥1/2, a Heisenberg bound for the fluctuations in particle number*n*and phase φ. For large enough*n*(a ‘photon number’) [Nφ]=−*i*for operators Nφ hence the bound: N has eigenvalues*n*. Because of the well-known stability of classical NLS solitons in optical fibres for very long distance optical communication (especially in the presence of amplifiers at distance separations ∼100 km), and because such classical ‘bits’ must in fact be*quantum*‘bits’, and therefore ‘qubits’, the quantum soliton solutions of the*quantum*attractive NLS equation seem worth investigating as such and in these terms — and this is what we shall do in this paper.### Keywords

Soliton Coherence### References

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