Preparation of engineered two-photon entangled states for multidimensional quantum information (original) (raw)
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Increasing the dimension in high-dimensional two-photon orbital angular momentum entanglement
Physical Review A, 2012
Any practical experiment utilising the innate D-dimensional entanglement of the orbital angular momentum (OAM) state space of photons is subject to the modal capacity of the detection system. We show that given such a constraint, the number of measured, entangled OAM modes in photon pairs generated by spontaneous parametric down-conversion (SPDC) can be maximised by tuning the phase-matching conditions in the SPDC process. We demonstrate a factor of 2 increase on the half-width of the OAM-correlation spectrum, from 10 to 20, the latter implying ≈ 50-dimensional two-photon OAM entanglement. Exploiting correlations in the conjugate variable, angular position, we measure concurrence values 0.96 and 0.90 for two phase-matching conditions, indicating bipartite, D-dimensional entanglement where D is tuneable.
High-dimensional entanglement with orbital-angular-momentum states of light
We engineer high-dimensional orbital-angular-momentum entanglement of photon pairs that emerge from a parametric down-conversion source. By means of two angular state analysers, in essence composed of a rotatable multi-sector phase plate and a single-mode fibre, we perform selective projective measurements that maximize the Shannon dimensionality D of the measured entanglement. The multi-sector phase plates have a binary phase profile along the azimuthal coordinate, and the arc sector sizes are optimized so as to maximize D.We find that the maximum dimensionality increases linearly with the number of sectors N. The potential of our method is illustrated with an experiment for N = 4, yielding D = 16.5.
Engineering two-photon high-dimensional states through quantum interference
Science advances, 2016
Many protocols in quantum science, for example, linear optical quantum computing, require access to large-scale entangled quantum states. Such systems can be realized through many-particle qubits, but this approach often suffers from scalability problems. An alternative strategy is to consider a lesser number of particles that exist in high-dimensional states. The spatial modes of light are one such candidate that provides access to high-dimensional quantum states, and thus they increase the storage and processing potential of quantum information systems. We demonstrate the controlled engineering of two-photon high-dimensional states entangled in their orbital angular momentum through Hong-Ou-Mandel interference. We prepare a large range of high-dimensional entangled states and implement precise quantum state filtering. We characterize the full quantum state before and after the filter, and are thus able to determine that only the antisymmetric component of the initial state remains...
Generation of entangled photon states by using linear optical elements
Physical Review A, 2002
We present a scheme to generate the polarization-entangled two-photon state 1 √ 2 (|H |V + |V |H), which is of much interest in the field of quantum information processing. Furthermore we demonstrate the capability of this concept in respect of a generalization to entangle N-photon states for interferometry and lithography. This scheme requires single-photon sources, linear optical elements and a multi-fold coincidence detection.
Creation and control of high-dimensional multi-partite classically entangled light
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Vector beams, non-separable in spatial mode and polarisation, have emerged as enabling tools in many diverse applications, from communication to imaging. This applicability has been achieved by sophisticated laser designs controlling the spin and orbital angular momentum, but so far is restricted to only two-dimensional states. Here we demonstrate the first vectorially structured light created and fully controlled in eight dimensions, a new state-of-the-art. We externally modulate our beam to control, for the first time, the complete set of classical Greenberger–Horne–Zeilinger (GHZ) states in paraxial structured light beams, in analogy with high-dimensional multi-partite quantum entangled states, and introduce a new tomography method to verify their fidelity. Our complete theoretical framework reveals a rich parameter space for further extending the dimensionality and degrees of freedom, opening new pathways for vectorially structured light in the classical and quantum regimes.
Demonstration of a programmable source of two-photon multiqubit entangled states
Physical Review A, 2010
We suggest and demonstrate a novel source of two-photon multipartite entangled states which exploits the transverse spatial structure of spontaneous parametric downconversion together with a programmable spatial light modulator (SLM). The 1D SLM is used to perform polarization entanglement purification and to realize arbitrary phase-gates between polarization and momentum degrees of freedom of photons. We experimentally demonstrate our scheme by generating two-photon three qubit linear cluster states with high fidelity using a diode laser pump with a limited coherence time and power on the crystal as low as ∼ 2.5mW.
Experimental photon entanglement in 11 x 11 dimensions for quantum information
arXiv (Cornell University), 2011
Quantum entanglement plays a vital role in many quantum information and communication tasks. Entangled states of higher dimensional systems are of great interest due to the extended possibilities they provide. For example, they allow the realisation of new types of quantum information schemes that can offer higher information-density coding and greater resilience to errors than can be achieved with entangled two-dimensional systems. Closing the detection loophole in Bell test experiments is also more experimentally feasible when higher dimensional entangled systems are used. We have measured previously untested correlations between two entangled photons to experimentally demonstrate high-dimensional entangled states. We show violations of Bell-type inequalities for two d-dimensional particles (qudits) with d reaching up to 11. Our experiments use photons entangled in orbital angular momentum (OAM), generated through spontaneous parametric down-conversion (SPDC), and manipulated using computer controlled holograms.
Quantum Information Transfer from Spin to Orbital Angular Momentum of Photons
Physical Review Letters, 2009
The optical "spin-orbit" coupling occurring in a suitably patterned nonuniform birefringent plate known as 'q-plate' allows entangling the polarization of a single photon with its orbital angular momentum (OAM). This process, in turn, can be exploited for building a bidirectional "spin-OAM interface", capable of transposing the quantum information from the spin to the OAM degree of freedom of photons and vice versa. Here, we experimentally demonstrate this process by singlephoton quantum tomographic analysis. Moreover, we show that two-photon quantum correlations such as those resulting from coalescence interference can be successfully transferred into the OAM degree of freedom.
AVS Quantum Science
Quantum mechanics is now a mature topic dating back more than a century. During its scientific development, it fostered many technological advances that now are integrated into our everyday lives. More recently, over the past few decades, the authors have seen the emergence of a second quantum revolution, ushering in control of quantum states. Here, the spatial modes of light, "patterns of light," hold tremendous potential: light is weakly interacting and so an attractive avenue for exploring entanglement preservation in open systems, while spatial modes of light offer a route to high dimensional Hilbert spaces for larger encoding alphabets, promising higher information capacity per photon, better security, and enhanced robustness to noise. Yet, progress in harnessing high dimensional spatial mode entanglement remains in its infancy. Here, the authors review the recent progress in this regard, outlining the core concepts in a tutorial manner before delving into the advances made in creation, manipulation, and detection of such quantum states. The authors cover advances in using orbital angular momentum as well as vectorial states that are hybrid entangled, combining spatial modes with polarization to form an infinite set of two-dimensional spaces: multidimensional entanglement. The authors highlight the exciting work in pushing the boundaries in both the dimension and the photon number, before finally summarizing the open challenges, and the questions that remain unanswered.
Two-photon entanglement of orbital angular momentum states
Physical Review A, 2002
We investigate the orbital angular momentum correlation of a photon pair created in a spontaneous parametric down-conversion process. We show how the conservation of the orbital angular momentum in this process results from phase matching in the nonlinear crystal.