Efficient and pure femtosecond-pulse-length source of polarization-entangled photons

Weston, Morgan M.; Chrzanowski, Helen M.; Wollmann, Sabine; Boston, Allen; Ho, Joseph; Shalm, Lynden K.; Verma, Varun B.; Allman, Michael S.; Nam, Sae Woo; Patel, Raj B.; Slussarenko, Sergei; Pryde, Geoff J.

doi:10.1364/oe.24.010869

Cited by 74 publications

(107 citation statements)

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“…SPDC from a nonlinear periodically poled KTP crystal (pp-KTP, poling period 46.20 µm) phase matched for type-II collinear operation produced degenerate photon pairs centred at 1550 nm wavelength and with ≈ 15 nm FWHM bandwidth. We used a pump waist size of 170 µm and a signal and idler collection waist size of 50 µm [21]. Together with the high efficiency SNSPDs [23], this allowed us to achieve symmetric heralding efficiencies of (82 ± 2)%.…”

Section: Appendix a Photon Source And Characterizationmentioning

confidence: 99%

“…This result was enabled by construction of a spontaneous parametric downconversion (SPDC) source [21], that was optimized for high photon transmission and required no spectral filtering in order to achieve high quantum interference visibility v. This allowed us to fully exploit the benefits of high-efficiency detector configuration [23], yielding an ultra-high heralding efficiency [22]-equivalent to the single-photon efficiency η. We emphasise that high-efficiency (95%) detection at 1550 nm wavelength has been available since 2008 [?…”

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confidence: 99%

“…We used collinear type-II parametric down-conversion, producing degenerate 1550 nm photon pairs [21]. Careful design and implementation of the source's output mode structure allowed us to achieve high fiber-coupling efficiency and state-of-the-art superconducting nanowire single photon detectors (SNSPDs) [23] provided high detection efficiency.…”

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confidence: 99%

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Unconditional violation of the shot-noise limit in photonic quantum metrology

et al. 2017

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Quantum metrology exploits quantum correlations to perform measurements with precision higher than can be achieved with classical approaches. Photonic approaches promise transformative advances in the family of interferometric phase measurement techniques, a vital toolset used to precisely determine quantities including distance, velocity, acceleration and various materials properties [1][2][3].Without quantum enhancement, the precision limit in determining an unknown optical phase ϕ-i.e. the minimum uncertainty ∆ϕ-is the shot noise limit (SNL): ∆ϕ SN L = 1/ √ n, where n is the number of resources (e.g. photons) used. Entangled photons promise measurement sensitivity surpassing the shot noise limit achievable with classical probes. The maximally phase-sensitive state is a path-entangled state of definite number of photons N . Despite theoretical proposals stretching back decades [3,4], no measurement using such photonic (definite photon number) states has unconditionally surpassed the shot noise limit: by contrast, all demonstrations have employed postselection to discount photon loss in the source, interferometer or detectors. Here, we use an ultra-high efficiency source and high efficiency superconducting photon detectors to respectively make and measure a two-photon instance of the maximally-phase-sensitive NOON state, and use it to perform unconditional phase sensing beyond the shot noise limit-that is, without artificially correcting for loss or any other source of imperfection. Our results enable quantum-enahanced phase measurements at low photon flux and open the door to the next generation of optical quantum metrology advances.It has been known for several decades that probing with various optical quantum states can achieve phase super-sensitivity, i.e measurement of the phase with an uncertainty below the SNL [3,4]. It has been shown theoretically that multi-photon entangled states, such as NOON states, may achieve super-sensitivity and can, in principle, saturate the Heisenberg limit (HL), the ultimate bound on sensitivity [3,4,7]. For this reason, they are of great interest for maximising the information that can be collected per photon, which is useful for investigating sensitive samples [8]. NOON states are superpositions of N photons across two arms of an interferometer, each of which is a single optical mode:We use the term photonic to refer to states like this, because they possess definite photon number, and these photons are counted in detection. By contrast, we exclude from term "photonic" schemes using states of indefinite photon number and continuous wave-like measurement, such as squeezed states and homodyne detection. Such techniques have genuinely beaten the SNL, e.g. refs [5,6], but work over narrow bandwidths and cannot directly achieve the theoretical maximal sensitivity per resource. Super-resolution, however, is not enough by itself to surpass the SNL [9,20]: a high interference fringe visibility, and high transmission and detection efficiency are also required-they must exceed the t...

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Section: Appendix a Photon Source And Characterizationmentioning

confidence: 99%

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Unconditional violation of the shot-noise limit in photonic quantum metrology

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“…3. For this, two SPDC sources are realised using a 775 nm Ti-sapphire picosecond-pulse-length pump laser and ppKTP (46.20 µm poling period) crystals cut for type-II collinear degenerate phase matching [26,27]. The photons are not entangled in polarisation.…”

Section: A Natural Question Is To Ask: What Is the Prevalence Of Suchmentioning

confidence: 99%

Dimensional Quantum Memory Advantage in the Simulation of Stochastic Processes

et al. 2019

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Stochastic processes underlie a vast range of natural and social phenomena [1,2]. Some processes such as atomic decay feature intrinsic randomness, whereas other complex processes, e.g. traffic congestion, are effectively probabilistic because we cannot track all relevant variables. To simulate a stochastic system's future behaviour, information about its past must be stored [3,4]and thus memory is a key resource. Quantum information processing promises a memory advantage for stochastic simulation [5][6][7][8][9][10][11][12][13][14][15] that has been validated in recent proof-of-concept experiments [16,17]. Yet, in all past works, the memory saving would only become accessible in the limit of a large number of parallel simulations [6,18], because the memory registers of individual quantum simulators had the same dimensionality as their classical counterparts. Here, we report the first experimental demonstration that a quantum stochastic simulator can encode the relevant information in fewer dimensions than any classical simulator, thereby achieving a quantum memory advantage even for an individual simulator. Our photonic experiment thus establishes the potential of a new, practical resource saving in the simulation of complex systems.

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“…Owing to the moderate heralding efficiency of the source, the range of input sizes which follow the linear amplification was restricted. However, this is not a fundamental restriction, as high-heralding-efficiency sources are starting to become available [24]. Furthermore, amplifiers for small quantum states can form component stages in a larger amplifier architecture [7,9].…”

Section: Resultsmentioning

confidence: 99%

Experimental noiseless linear amplification using weak measurements

Boston

Palsson

et al. 2016

New J. Phys.

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The viability of quantum communication schemes rely on sending quantum states of light over long distances. However, transmission loss can degrade the signal strength, adding noise. Heralded noiseless amplification of a quantum signal can provide a solution by enabling longer direct transmission distances and by enabling entanglement distillation. The central idea of heralded noiseless amplification-a conditional modification of the probability distribution over photon number of an optical quantum state-is suggestive of a parallel with weak measurement: in a weak measurement, learning partial information about an observable leads to a conditional back-action of a commensurate size. Here we experimentally investigate the application of weak, or variable-strength, measurements to the task of heralded amplification, by using a quantum logic gate to weakly couple a small single-optical-mode quantum state (the signal) to an ancilla photon (the meter). The weak measurement is carried out by choosing the measurement basis of the meter photon and, by conditioning on the meter outcomes, the signal is amplified. We characterise the gain of the amplifier as a function of the measurement strength, and use interferometric methods to show that the operation preserves the coherence of the signal.

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Efficient and pure femtosecond-pulse-length source of polarization-entangled photons

Cited by 74 publications

References 50 publications

Unconditional violation of the shot-noise limit in photonic quantum metrology

Unconditional violation of the shot-noise limit in photonic quantum metrology

Dimensional Quantum Memory Advantage in the Simulation of Stochastic Processes

Experimental noiseless linear amplification using weak measurements

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