Ultrabright source of polarization-entangled photons

Kwiat, Paul G.; Waks, Edo; White, A. G.; Appelbaum, Ian; Eberhard, Philippe

doi:10.1103/physreva.60.r773

Cited by 1,117 publications

(925 citation statements)

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“…Photon source: Entangled photon pairs, spectrally degenerate at 808 nm, were generated in a Type 1 spontaneous parametric down conversion source, with a 404 nm CW laser was focused to a 40 µm waist in a pair of crossed BiB 3 O 6 (Bismuth Triborate) non linear crystals 29 . Photons were spectrally filtered with high transmission interference filters of FWHM 3nm, then collected into polarisation maintaining optical fibres (PMFs).…”

Section: Methodsmentioning

confidence: 99%

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Experimental realization of Shor's quantum factoring algorithm using qubit recycling

et al. 2012

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Quantum computational algorithms exploit quantum mechanics to solve problems exponentially faster than the best classical algorithms 1-3 . Shor's quantum algorithm 4 for fast number factoring is a key example and the prime motivator in the international effort to realise a quantum computer 5 . However, due to the substantial resource requirement, to date, there have been only four small-scale demonstrations 6-9 . Here we address this resource demand and demonstrate a scalable version of Shor's algorithm in which the n qubit control register is replaced by a single qubit that is recycled n times: the total number of qubits is one third of that required in the standard protocol [10][11][12] . Encoding the work register in higher-dimensional states, we implement a two-photon compiled algorithm to factor N = 21. The algorithmic output is distinguishable from noise, in contrast to previous demonstrations. These results point to larger-scale implementations of Shor's algorithm by harnessing scalable resource reductions applicable to all physical architectures.Shor's factoring algorithm consists of a quantum order finding algorithm, preceded and succeeded by various classical routines. While the classical tasks are known to be efficient on a classical computer, order finding is understood to be intractable classically. However, it is known that this part of the algorithm can be performed efficiently on a quantum computer. To determine the prime factors of an odd integer N , one chooses a coprime of N , x. The order r relates x to N according to x r mod N = 1, and can be used to obtain the factors, given by the greatest common divisor gcd(x r 2 ± 1, N ). The quantum order finding circuit involves two registers: a work register and a control register. In the standard protocol, the work register performs modular arithmetic with m = log 2 N qubits, enough to encode the number N , and the n qubit control register provides the algorithmic output, with n bits of precision.Measuring the control register in the computational basis will yield a result of k2 n /r where k is an integer between 0 and r − 1, with the value of k occurring probabilistically. Dividing the result by 2 n gives the first n bits of k/r and r may be found with classical processing, using the continued fraction algorithm. For large n, and a perfectly functioning circuit, the output probability distribution of the control register is a series of well defined peaks at values of k2 n /r (Fig. 1b). (See Appendix for details.)Here we implement an iterative version of the order finding algorithm 10,11 , in which the control register contains only a single qubit which is recycled n times, using a sequence of measurement and feed-forward operations, with each step providing an additional bit of precision (Fig. 1a). Reducing the number of qubits in quantum simulations and quantum chemistry has been achieved with recursive phase estimation 13-16 , while ground state projections have been demonstrated by exploiting similar techniques in NMR 17 .The iterative version of...

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Section: Methodsmentioning

confidence: 99%

“…The circuit was constructed with Jamin-Lebedeff polarisation interferometers in a calcite beam displacer architecture, chosen to provide interferometric stability. Photons were generated with a polarisation entangled spontaneous parametric down conversion source 29 (See Methods for further experimental details).…”

Section: Figmentioning

confidence: 99%

Experimental realization of Shor's quantum factoring algorithm using qubit recycling

et al. 2012

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“…Typical down-conversion sources using beta barium borate (BBO) crystals [5,6,7] are not suitable for narrowband applications such as quantum memory loading because of their large bandwidths of 1-10 nm. These sources also have relatively low flux, partly because of inefficient collection of the output photons in their emission cone and partly because of the small nonlinear coefficient of BBO.…”

Section: Introductionmentioning

confidence: 99%

Efficient and spectrally bright source of polarization-entangled photons

et al. 2005

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We demonstrate an efficient fiber-coupled source of nondegenerate polarization-entangled photons at 795 and 1609 nm using bidirectionally pumped parametric down-conversion in bulk periodically poled lithium niobate. The single-mode source has an inferred bandwidth of 50 GHz and a spectral brightness of 300 pairs/s/GHz/mW of pump power that is suitable for narrowband applications such as entanglement transfer from photonic to atomic qubits.

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“…It thus provides a simple and fascinating alternative to complement the latter. With ease of manipulation and control, the nearly perfect quality of this source allows to perform highly faithful and precise quantum computing.To generate the state we use the technique developed in previous experiments [12] with type-I spontaneous parametric down-conversion (SPDC) source [20]. The experimental setup is shown in Fig.…”

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confidence: 99%

“…To generate the state we use the technique developed in previous experiments [12] with type-I spontaneous parametric down-conversion (SPDC) source [20]. The experimental setup is shown in Fig.…”

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confidence: 99%

Experimental Realization of One-Way Quantum Computing with Two-Photon Four-Qubit Cluster States

et al. 2007

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We report an experimental realization of one-way quantum computing on a two-photon four-qubit cluster state. This is accomplished by developing a two-photon cluster state source entangled both in polarization and spatial modes. With this special source, we implemented a highly efficient Grover's search algorithm and high-fidelity two qubits quantum gates. Our experiment demonstrates that such cluster states could serve as an ideal source and a building block for rapid and precise optical quantum computation.PACS numbers: 03.67. Lx, 03.67.Mn, 42.50.Dv Highly entangled multipartite states, so-called cluster states, have recently raised enormous interest in quantum information processing (QIP). These sorts of states are crucial as a fundamental resource and a building block aimed at one-way universal quantum computing [1]. They are also essential elements for various quantum error correction codes and quantum communication protocols [2]. Moreover, the entanglements are shown to be robust against decoherence [3], and persistent against loss of qubits [1], and thus are exceptionally well suited for quantum computing and many tasks [1,2]. Considerable efforts have been made toward generating and characterizing cluster state in linear optics [4,5,6,7,8,9]. Recently the principal feasibility of a one-way quantum computing model has been experimentally demonstrated through 4-photon cluster states successfully [7,8,10].So far, preparing photonic cluster state still suffers from several serious limitations. Due to the probabilistic nature and Poissonian distribution of the parametric down-conversion process, the generation rate of 4-photon cluster states is quite low [5,6,7,8], and largely restricts speed of computing. Besides, the quality and fidelity of prepared cluster states are relatively low [6,7,8], which are difficult to be improved substantially. These disadvantages consequently impose great challenges of advancement even for few-qubit quantum computing.Fortunately, motivated by the progress that an important type of states termed hyper-entangled states have been experimentally generated [11,12,13,14], we have the possibility to produce a new type of cluster state (2-photon 4-qubit cluster state) with nearly perfect fidelity and high generation rate. The hyper-entangled states have been used to test "All-Versus-Nothing" (AVN) quantum nonlocality [11,12,15], and are shown to lead to an enhancing violation of local realism [16,17]. The states also enable to perform complete deterministic Bell state analysis [18] as demonstrated in [14,19].In this Letter we report an experimental realization of one-way quantum computing with such a 2-photon 4-qubit cluster state. The key idea is to develop and employ a bright source which produces a 2-photon state entangled both in polarization and spatial modes. We are thus able to implement the Grover's algorithm and quantum gates with excellent performances. The genuine four-partite entanglement and high fidelity of better than 88% are characterized by an optimal entanglement w...

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Ultrabright source of polarization-entangled photons

Cited by 1,117 publications

References 37 publications

Experimental realization of Shor's quantum factoring algorithm using qubit recycling

Experimental realization of Shor's quantum factoring algorithm using qubit recycling

Efficient and spectrally bright source of polarization-entangled photons

Experimental Realization of One-Way Quantum Computing with Two-Photon Four-Qubit Cluster States

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