iBet uBet web content aggregator. Adding the entire web to your favor.
iBet uBet web content aggregator. Adding the entire web to your favor.



Link to original content: https://pubmed.ncbi.nlm.nih.gov/21098305
Teleportation-based realization of an optical quantum two-qubit entangling gate - PubMed Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2010 Dec 7;107(49):20869-74.
doi: 10.1073/pnas.1005720107. Epub 2010 Nov 22.

Teleportation-based realization of an optical quantum two-qubit entangling gate

Wei-Bo Gao  1 , Alexander M Goebel, Chao-Yang Lu, Han-Ning Dai, Claudia Wagenknecht, Qiang Zhang, Bo Zhao, Cheng-Zhi Peng, Zeng-Bing Chen, Yu-Ao Chen, Jian-Wei Pan
Affiliations

Teleportation-based realization of an optical quantum two-qubit entangling gate

Wei-Bo Gao et al. Proc Natl Acad Sci U S A. .

Abstract

In recent years, there has been heightened interest in quantum teleportation, which allows for the transfer of unknown quantum states over arbitrary distances. Quantum teleportation not only serves as an essential ingredient in long-distance quantum communication, but also provides enabling technologies for practical quantum computation. Of particular interest is the scheme proposed by D. Gottesman and I. L. Chuang [(1999) Nature 402:390-393], showing that quantum gates can be implemented by teleporting qubits with the help of some special entangled states. Therefore, the construction of a quantum computer can be simply based on some multiparticle entangled states, Bell-state measurements, and single-qubit operations. The feasibility of this scheme relaxes experimental constraints on realizing universal quantum computation. Using two different methods, we demonstrate the smallest nontrivial module in such a scheme--a teleportation-based quantum entangling gate for two different photonic qubits. One uses a high-fidelity six-photon interferometer to realize controlled-NOT gates, and the other uses four-photon hyperentanglement to realize controlled-Phase gates. The results clearly demonstrate the working principles and the entangling capability of the gates. Our experiment represents an important step toward the realization of practical quantum computers and could lead to many further applications in linear optics quantum information processing.

PubMed Disclaimer

Conflict of interest statement

The authors declare no conflict of interest.

Figures

Fig. 1.
Fig. 1.
Quantum circuit for teleporting two qubits through a C-NOT gate and a C-Phase gate. (A) The input consisting of the target qubit |T〉1 and control qubit |C〉2 can be arbitrarily chosen. BSMs are performed between the input states and the left qubits of the special entangled state |χ〉. Depending on the outcome of the BSMs, local unitary operations (U,U′) are applied on the remaining qubits of |χ〉, which then form the output |out〉 = UC-NOT|T〉1|C〉2 or |out〉 = UC-Phase|T〉1|C〉2. (B) The special entangled state |χ〉 can be constructed by performing a C-NOT gate on two Bell pairs, with formula image. See SI Text for details.
Fig. 2.
Fig. 2.
A schematic diagram of the experimental setup. We frequency double a mode-locked Ti∶sapphire laser system to create a high-intensity pulsed UV laser beam at a central wavelength of 390 nm, a pulse duration of 180 fs, and a repetition rate of 76 MHz. The UV beam successively passes through three β-barium borate (BBO) crystals to generate three polarization entangled photon pairs via type-II spontaneous parametric down-conversion (27). At the first BBO the UV generates a photon pair in modes 1 and 2 (i.e., the input consisting of the target and control qubit). After the crystal, the UV is refocused onto the second BBO to produce another entangled photon pair in modes 3 and 4 and correspondingly for modes 5 and 6. Photons 4 and 6 are then overlapped at a PPBS and together with photons 3 and 5 constitute the cluster state. Two PPBSs are used for state normalization. The prisms are mounted on step motors and are used to compensate the time delay for the interference at the PPBS and the BSMs. A BSM is performed by overlapping two incoming photons on a PBS and two subsequent PAs. A PA projects the photon onto an unambiguous polarization depending on the basis determined by a half- or quarter-wave plate (HWP or QWP). The photons are detected by silicon avalanched single-photon detectors. Coincidences are recorded with a coincidence unit clocked by the infrared laser pulses. Polarizers (Pol.) are polarizers used to prepare the input state, and narrow-band filters (Filter) with ΔFW HM = 3.2 nm are used to obtain a better spectral interference.
Fig. 3.
Fig. 3.
Experimental results for teleportation-based C-NOT gate. (A) Experimental results for truth table of the C-NOT gate. The first qubit is the target and the second is the control qubit. In the data, we considered the corresponding unitary transformation depending on the type of coincidence at the BSM (| + 〉| + 〉, | + 〉| - 〉, | - 〉| + 〉, | - 〉| - 〉). The average fidelity for the truth table is 0.72 ± 0.05. (B) Experimental results for fidelity measurements of entangled output states. Basis |H〉/|V〉 is used for the measurements of formula image; (C) | + 〉/| - 〉 for formula image; (D) formula image for formula image. The measured expectation values are (B) 0.403 ± 0.066, (C) 0.462 ± 0.057, and (D) -0.434 ± 0.062. All errors are statistical and correspond to ± 1 standard deviations.
Fig. 4.
Fig. 4.
Schematic of the experimental setup. (A) Femtosecond UV pulses pass through two BBO crystals to create two pairs of entangled photons. Two polarizers are inserted in the arms of 3 and 4 to prepare single photons in formula image. (B) Photons 3 and 5 are sent through Mach–Zehnder-type interferometers to perform the spatial-polarization BSM. Polarization and spatial qubit transformation happens at the first PBS, and BSM happens at the second PBS. (C) In the experiment, we use an ultrastable Sagnac configuration interferometer to satisfy the desired high stability.
Fig. 5.
Fig. 5.
Experimental evaluation of the quality of the C-phase gate. Data for Fz4′x6′ and Fx4′z6′ are measured for 22.5 min, respectively, and data for Fx4′x6′ are measured for 45 min. (A) Experimental values for measurements of Fz4′x6′. (B) Experimental values for measurements of Fx4′z6′. (C) Experimental values for measurements of Fx4′x6′. (D) Theoretical values for Fz4′x6′. (E) Theoretical values for Fx4′z6′. (F) Theoretical values for Fx4′x6′.
Fig. 6.
Fig. 6.
The fidelity with the expected state before and after the correction operations. The input control and target qubit are both in the state | + 〉, so the output state is expected to be formula image. The fidelity is much higher after correction operations. The 16 cases correspond to the 16 different outputs of the two BSMs (see Table S1).
See this image and copyright information in PMC

Similar articles

See all similar articles

Cited by

See all "Cited by" articles

References

    1. Knill E, Laflamme R, Milburn GJ. A scheme for efficient quantum computation with linear optics. Nature. 2001;409:46–52. - PubMed
    1. Gottesman D, Chuang IL. Demonstrating the viability of universal quantum computation using teleportation and single-qubit operations. Nature. 1999;402:390–393.
    1. Bennett CH, et al. Teleporting an unknown quantum state via dual classical and Einstein-Podolsky-Rosen channels. Phys Rev Lett. 1993;70:1895–1899. - PubMed
    1. Bouwmeester D, et al. Experimental quantum teleportation. Nature. 1997;390:575–579.
    1. O’Brien JL, et al. Demonstration of an all-optical quantum controlled-NOT gate. Nature. 2003;426:264–267. - PubMed

LinkOut - more resources