Fiber-assisted detection with photon number resolution

Abstract

We report the development of a photon-number resolving detector based on a fiber-optical setup and a pair of standard avalanche photodiodes. The detector is capable of resolving individual photon numbers, and operates on the well-known principle by which a single mode input state is split into a large number (eight) of output modes. We reconstruct the photon statistics of weak coherent input light from experimental data, and show that there is a high probability of inferring the input photon number from a measurement of the number of detection events on a single run.Many quantum information strategies require the preparation of nonclassical states. For example, the method of linear optical quantum computing proposed by Knill, Laflamme, and Milburn [1] demands the preparation of single photon states as well as maximally entangled photon multiplets. A number of schemes have been proposed for the preparation of such states, including single photon emitters [2,3,4] and conditionally prepared photon pairs from parametric downconversion [5,6,7]. Conditional state preparation requires the ability to distinguish states of different photon number, which is not possible using conventional photodetectors. Photon number resolution is also desirable to enhance the security of quantum cryptographic schemes [8,9]. In this case it is important to measure the photon statistics of the source at the sending and receiving stations. For implementations that use weak coherent states this means distinguishing between the detection of, say, one or two photons.According to the quantum theory of photodetection, the signal obtained from an ideal noise-free detector has a discrete form corresponding to the absorption of an integer number of quanta from the incident radiation. In practice, however, the granularity of the output signal is concealed by the noise of the detection mechanism. When very low light levels are detected using devices with single-photon sensitivity such as photomultipliers or Geiger-mode operated avalanche photodiodes (APDs), the electronic signal can be reliably converted into a binary message telling us with high efficiency whether an absorption event has occurred or not. However, the intrinsic noise of the gain mechanism necessary to bring the initial energy of absorbed radiation to the macroscopic level completely masks the information on exactly how many photons have triggered that event.There are several methods for constructing photon number resolving detectors. Among those demonstrated to date are the segmented photomultiplier [10], the superconducting bolometer [11], and the superconducting transimpedance amplifier [12]. These detectors operate at cryogenic temperatures and have single photon quantum efficiencies ranging from about 20% for the superconducting devices to approximately 70% in the case of the segmented photomultiplier. On the other hand, conventional room temperature APDs have intrinsic quantum efficiencies up to 80%, though they respond only to the presence or absence of radiation. The ease of...

True photocounting statistics of multiple on-off detectors

“…However, simultaneous clicks of some detector deliver additional information about the photon number distribution of the incident quantum state. Another experimentally realized PNR detector is the multiplex detection scheme, which is based on a multiple 50:50 splitting of a signal into weaker ones [20][21][22][23][24][25]. The incoming signal can be split and detected in different spatial or temporal -time-multiplexing -modes or bins.…”

Photon-number-resolution with sub-30-ps timing using multi-element superconducting nanowire single photon detectors

“…One often cited advantage of the multiplexing approach in general is that it can be used to transform any single-photon-sensitive detector technology into a photon-number-resolving detector, including technologies that operate near room temperature. Applications requiring compact photonnumber-resolving detectors may benefit from this approach, which has been demonstrated for both spatial [12] and temporal [13][14] multiplexing. However, one advantage unique to spatial multiplexing is the ability to create a photon-number-resolving detector with higher performance, particularly in terms of the maximum counting rate and timing resolution.…”

“…This approach has been proposed and demonstrated both for spatial multiplexing [11][12] and for temporal multiplexing [13][14]. Using the multiplexing approach, the fidelity of the photon-number-resolution measurement is again limited in part by the detection efficiency.…”

Photon-number-resolving detection using time-multiplexing

“…In this paper, we provide a detailed analysis of two recent experiments [17,18] which follow the main concept developed in [15], but avoids the need for optical switches [19,20]. The basic idea is very similar to the detector cascade concept [21], which uses 50/50 beam splitters to split a pulse into N spatial modes, each of which is monitored with an APD.…”