No Arabic abstract
A scheme for the enhanced generation of higher photon-number states is realized, using an optical time-multiplexing setting that exploits a parametric down-conversion source for an iterative state generation. We use a quantum feedback mechanism for already generated photons to induce self-seeding of the consecutive nonlinear process, enabling us to coherently add photons to the light that propagates in the feedback loop. The addition can be carried out for any chosen number of round trips, resulting in a successive buildup of multiphoton states. Our system is only limited by loop losses. The looped design is rendered possible by a carefully engineered waveguide source that is compatible with and preserves the shape of the propagating mode. We compare the fidelities and success probabilities of our protocol with the common direct heralding of photon-number states. This comparison reveals that, for same the fidelity, our feedback-based setup significantly enhances success probabilities, being vital for an efficient utilization in quantum technologies. Moreover, quantum characteristics of the produced states are analyzed, and the flexibility of producing higher photon-number states with our setup beyond the common direct heralding is demonstrated.
We demonstrate a Fock-state filter which is capable of preferentially blocking single photons over photon pairs. The large conditional nonlinearities are based on higher-order quantum interference, using linear optics, an ancilla photon, and measurement. We demonstrate that the filter acts coherently by using it to convert unentangled photon pairs to a path-entangled state. We quantify the degree of entanglement by transforming the path information to polarisation information, applying quantum state tomography we measure a tangle of T=(20+/-9)%.
Quantum simulations are becoming an essential tool for studying complex phenomena, e.g. quantum topology, quantum information transfer, and relativistic wave equations, beyond the limitations of analytical computations and experimental observations. To date, the primary resources used in proof-of-principle experiments are collections of qubits, coherent states or multiple single-particle Fock states. Here we show the first quantum simulation performed using genuine higher-order Fock states, with two or more indistinguishable particles occupying the same bosonic mode. This was implemented by interfering pairs of Fock states with up to five photons on an interferometer, and measuring the output states with photon-number-resolving detectors. Already this resource-efficient demonstration reveals new topological matter, simulates non-linear systems and elucidates a perfect quantum transfer mechanism which can be used to transport Majorana fermions.
We present a new mechanism that harnesses extremely weak Kerr-type nonlinearities in a single driven cavity to deterministically generate single photon Fock states, and more general photon-blockaded states. Our method is effective even for nonlinearities that are orders-of-magnitude smaller than photonic loss. It is also completely distinct from so-called unconventional photon blockade mechanisms, as the generated states are non-Gaussian, exhibit a sharp cut-off in their photon number distribution, and can be arbitrary close to a single-photon Fock state. Our ideas require only standard linear and parametric drives, and is hence compatible with a variety of different photonic platforms.
The two-photon ladder climbing (successive two-photon Landau-Zener-type transitions) in a chirped quantum nonlinear oscillator and its classical limit (subharmonic autoresonance) are discussed. An isomorphism between the chirped quantum-mechanical one and two-photon resonances in the system is used in calculating the threshold for the phase-locking transition in both the classical and quantum limits. The theory is tested by solving the Schrodinger equation in the energy basis and illustrated via the Wigner function in phase space.
When the background density in a bounded plasma is modulated in time, discrete modes become coupled. Interestingly, for appropriately chosen modulations, the average plasmon energy might be made to grow in a ladder-like manner, achieving up-conversion or down-conversion of the plasmon energy. This reversible process is identified as a classical analog of the effect known as quantum ladder climbing, so that the efficiency and the rate of this process can be written immediately by analogy to a quantum particle in a box. In the limit of densely spaced spectrum, ladder climbing transforms into continuous autoresonance; plasmons may then be manipulated by chirped background modulations much like electrons are autoresonantly manipulated by chirped fields. By formulating the wave dynamics within a universal Lagrangian framework, similar ladder climbing and autoresonance effects are predicted to be achievable with general linear waves in both plasma and other media.