Deterministic quantum splitter based on time-reversed Hong-Ou-Mandel interference

Abstract

By utilizing a fiber-based indistinguishable photon-pair source in the 1.55 m telecommunications band ͓J. Chen et al., Opt. Lett. 31, 2798 ͑2006͔͒, we present the first, to the best of our knowledge, deterministic quantum splitter based on the principle of time-reversed Hong-Ou-Mandel quantum interference. The deterministically separated identical photons' indistinguishability is then verified by using a conventional Hong-Ou-Mandel quantum interference, which exhibits a near-unity dip visibility of 94± 1%, making this quantum splitter useful for various quantum information processing applications.The nascent field of quantum information science, motivated by the extraordinary computing power of a full-fledged quantum computer, naturally selects photons-the fundamental energy packets of the electromagnetic field-as the carrier of quantum information from one computing node to another, a task typically associated with quantum communication. The omnipresent telecommunication fibers constitute the quantum channels for quantum cryptography ͓1͔, quantum gambling ͓2͔, and quantum games ͓3͔, which utilize remote sharing of quantum entanglement as a resource. In addition, indistinguishable photons-photons having identical wave packets-play a major role in the arena of linear optical quantum computing ͓4͔. Therefore a telecom-band indistinguishable photon-pair source is particularly useful for the above quantum-information-processing ͑QIP͒ tasks. The traditional method of producing such photons-spontaneous parametric down-conversion in second-order ͑ ͑2͒ ͒ nonlinear crystals ͓5͔-faces formidable engineering challenges when these photons are launched into a single-mode optical fiber for long-distance transmission or mode cleansing. Large coupling losses inevitably occur due to mode mismatch ͓6͔, limiting the usefulness of such a source. Recently we demonstrated a fiber-based source of indistinguishable photon pairs at a telecom-band wavelength near 1550 nm that utilizes the third-order ͑ ͑3͒ ͒ nonlinear process of four-wave mixing ͑FWM͒ ͓7͔ in the fiber itself. This approach automatically takes care of the aforementioned mode-matching issue, since the photonic spatial mode of the generated photon pair is the same as that of standard optical fiber.Four-wave mixing is a third-order process mediated by the Kerr nonlinearity of optical fiber, wherein two pump photons annihilate to give birth to a pair of time-energy entangled daughter photons, usually denoted as signal and idler. Energy conservation as well as momentum conservation are obeyed during the FWM process: p1 + p2 = s + i , and k ជ p1 + k ជ p2 = k ជ s + k ជ i , where j and k ជ j stand for the frequency and wave vector of the jth photon, and the subscripts p1, p2, s, and i denote the two pump photons, the signal photon, and the idler photon, respectively. Our group has previously demonstrated generation ͓9,10͔, distribution ͓11͔, and storage ͓12͔ of nondegenerate photon pairs ͑s i͒ with a singlefrequency pump pulse ͑p1= p2͒. More recently, we have also achieved success...

CMOS-compatible photonic devices for single-photon generation

“…Frequency-degenerate photon-pair generation via SFWM has been demonstrated in optical fibers previously [48,49]. Very recently, several groups including us have reported the on-chip demonstrations based on silicon nanowires [17], PhC slow-light waveguides [39], and microrings [38,40].…”

On-chip quantum interference between silicon photon-pair sources

“…[22] By considering the degenerate pair case, and specifically setting φ = 0 or φ = π 2 , we can obtain either state at the output:…”

Deterministic separation of arbitrary photon pair states in integrated quantum circuits

“…The first demonstration of time-reversed HOM interference for the purpose of deterministic pair separation was reported using a nonlinear fiber Sagnac loop in 2007 by Chen, Lee, and Kumar [22]. Each propagation direction then became a source of identical photon pairs leading to quantum interference between the CW and CCW directions.…”

“…In much the same way, quantum interference between two identical sources of photon pairs can be used to achieve the reverse effect: the anticoalescence of bunched states into anti-bunched states. Such interference-facilitated pair separation (IFPS) was realized first in fiber Sagnac loops [22][23][24] and more recently on-chip [12,14] by coherently pumping two photon pair sources, e.g. denoted A and B, to create an approximate NOON-type state of the form |Ψ = |ψ A |0 B + e iθ |0 A |ψ B where θ represents a stable relative phase, |ψ a photon pair, and |0 the vacuum.…”