The paradox of the many-state catastrophe of fundamental limits and the three-state conjecture

Abstract

The calculation of the fundamental limits of nonlinear susceptibilities posits that when a quantum system has a nonlinear response at the fundamental limit, only three energy eigenstates contribute to the first and second hyperpolarizability. This is called the three-level ansatz and is the only unproven assumption in the theory of fundamental limits. All calculations that are based on direct solution of the Schrodinger equation yield intrinsic hyperpolarizabilities less than 0.709 and intrinsic second hyperpolarizabilities less than 0.6. In this work, we show that relaxing the three-level ansatz and allowing an arbitrary number of states to contribute leads to divergence of the optimized intrinsic hyperpolarizability in the limit of an infinite number of states - what we call the many-state catastrophe. This is not surprising given that the divergent systems are most likely not derivable from the Schrodinger equation, yet obey the sum rules. The sums rules are the second ingredient in limit theory, and apply also to systems with more general Hamiltonians. These exotic Hamiltonians may not model any real systems found in nature. Indeed, a class of transition moments and energies that come form the sum rules do not have a corresponding Hamiltonian that is expressible in differential form. In this work, we show that the three-level ansatz acts as a constraint that excludes many of the nonphysical Hamiltonians and prevents the intrinsic hyperpolarizability from diverging. We argue that this implies that the true fundamental limit is smaller than previously calculated. Since the three-level ansatz does not lead to the largest possible nonlinear response, contrary to its assertion, we propose the intriguing possibility that the three-level ansatz is true for any system that obeys the Schrodinger equation, yet this assertion may be unprovable.

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• Pushing the hyperpolarizability to the limit
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• A new dipole-free sum-over-states expression for the second hyperpolarizability
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Cited by in corpus (12)

• Exact fundamental limits of the first and second hyperpolarizabilities
• Physics of the fundamental limits of nonlinear optics: A theoretical perspective
• Dressed quantum graphs with optical nonlinearities approaching the fundamental limit
• Lowest-order relativistic corrections to the fundamental limits of nonlinear-optical coefficients
• Optimization of eigenstates and spectra for quasi-linear nonlinear optical systems
• Optimum topology of quasi-one dimensional nonlinear optical quantum systems
• Using excited states and degeneracies to enhance the electric polarizability and first hyperpolarizability
• A Heuristic Approach for Treating Pathologies of Truncated Sum Rules in Limit Theory of Nonlinear Susceptibilities
• Polynomial potentials determined from the energy spectrum and transition dipole moments that give the largest hyperpolarizabilities
• Three-state interactions determine the second-order nonlinear optical response
• Static hyperpolarizability of space-fractional quantum systems
• Topological control of the nonlinear-optical response of hybrid quantum systems