Photon Number Resolving Detector Research Articles

Multi-mode Gaussian state analysis with total-photon counting

The continuing improvement in the qualities of photon-number-resolving (PNR) detectors opens new possibilities for measuring quantum states of light. In this work we consider the question of what properties of an arbitrary multi-mode Gaussian state are determined by a single PNR detector that measures total-photon number. We find an answer to this question in the ideal case where the exact photon-number probabilities are known. We show that the quantities determined by the total-photon-number distribution are the spectrum of the covariance matrix, the absolute displacement in each eigenspace of the covariance matrix, and nothing else. In the case of pure Gaussian states, the spectrum determines the squeezing parameters.

Algorithm of quantum engineering of large-amplitude high-fidelity Schrödinger cat states

We present an algorithm of quantum engineering of large-amplitude ge 5 high-fidelity ge 0.99 even/odd Schrödinger cat states (SCSs) using a single mode squeezed vacuum (SMSV) state as resource. Set of k beam splitters (BSs) with arbitrary transmittance and reflectance coefficients sequentially following each other acts as a hub that redirects a multiphoton state into the measuring modes simultaneously measured by photon number resolving (PNR) detectors. We show that the multiphoton state splitting guarantees significant increase of the success probability of the SCSs generator compared to its implementation in a single PNR detector version and imposes less requirements on ideal PNR detectors. We prove that the fidelity of the output SCSs and its success probability are in conflict with each other (which can be quantified) in a scheme with ineffective PNR detectors, especially when subtracting large (say, 100) number of photons, i.e., increasing the fidelity to perfect values leads to a sharp decrease in the success probability. In general, the strategy of subtracting up to 20 photons from initial SMSV in setup with two BSs is acceptable for achieving sufficiently high values of the fidelity and success probability at the output of the generator of the SCSs of amplitude le 3 with two inefficient PNR detectors.

Time Binning Method for Nonpulsed Sources Characterization With a Superconducting Photon Number Resolving Detector

Time Binning Method for Nonpulsed Sources Characterization With a Superconducting Photon Number Resolving Detector

Quantum non-Gaussianity certification of photon number-resolving detectors.

We report on direct experimental certification of the quantum non-Gaussian character of a photon number-resolving detector. The certification protocol is based on an adaptation of the existing quantum non-Gaussianity criteria for quantum states to quantum measurements. In our approach, it suffices to probe the detector with a vacuum state and two different thermal states to test its quantum non-Gaussianity. The certification is experimentally demonstrated for the detector formed by a spatially multiplexed array of ten single-photon avalanche photodiodes. We confirm the quantum non-Gaussianity of POVM elements Π^m associated with the m-fold coincidence counts, up to m = 7. The experimental ability to certify from the first principles the quantum non-Gaussian character of Π^m is for large m limited by low probability of the measurement outcomes, especially for vacuum input state. We find that the injection of independent Gaussian background noise into the detector can be helpful and may reduce the measurement time required for reliable confirmation of quantum non-Gaussianity. In addition, we modified and experimentally verified the quantum non-Gaussianity certification protocol employing a third thermal state instead of a vacuum to speed up the whole measurement. Our findings demonstrate the existence of efficient tools for the practical characterization of fundamental non-classical properties and benchmarking of complex optical quantum detectors.

High-speed photon-number-resolving detection via a GHz-gated SiPM.

Silicon photomultipliers (SiPMs) constitute a promising candidate for photon-number-resolving (PNR) detection via spatial multiplexing, which offer advantages like high integration and low cost. Up to date, there has been continuous endeavor in boosting the PNR performances, particularly on the resolved photon numbers and operation speed. Here, we demonstrate a GHz-gated SiPM in the Geiger mode, which allows to quench the photon-induced avalanche signal within 1 ns. Specifically, the capacitive response of the SiPM has been effectively suppressed by combining the low-pass filtering and self-differencing technique, which facilitates a high-fidelity extraction of the avalanche pulse with a reduced error rate. Consequently, high-speed PNR detection has been manifested in resolving up to 14 photons for laser pulses at a repetition rate of 40 MHz. The presented high-speed PNR detector may open up new possibilities to implement applications such as large-dynamic-range optical sensing, high-capacity optical communication, and multi-photon quantum optics.

Improved pulse discrimination for a superconducting series nanowire detector by applying a digital matched filter

Photon number resolving (PNR) is an important capacity for detectors working in quantum and classical applications. Although a conventional superconducting nanowire single-photon detector (SNSPD) is not a PNR detector, by arranging nanowires in a series array and multiplexing photons over space, such series PNR-SNSPD can gain quasi-PNR capacity. However, the accuracy and maximum resolved photon number are both limited by the signal-to-noise ratio (SNR) of the output pulses. Here, we introduce a matched filter, which is an optimal filter in terms of SNR. Experimentally, the normalized spacing between pulse amplitudes from adjacent photon number detections increased by a maximum factor of 2.1 after the matched filter. Combining with a cryogenic amplifier to increase SNR further, such spacing increased by a maximum factor of 5.3. In contrast to a low pass filter, the matched filter gave better SNRs while maintaining low timing jitters. The minimum timing jitter of 55 ps was obtained experimentally. Our results suggest that the matched filter is a useful tool for improving the performance of the series PNR-SNSPD. The maximum resolved photon number can be expected to reach 65 or even larger.

Single-shot number-resolved detection of microwave photons with error mitigation

Single-photon detectors are ubiquitous and integral components of photonic quantum cryptography, communication, and computation. Many applications, however, require not only detecting the presence of any photons, but distinguishing the number present with a single shot. Here, we implement a single-shot, high-fidelity photon number-resolving detector of up to 15 microwave photons in a cavity-qubit circuit QED platform. This detector functions by measuring a series of generalized parity operators which make up the bits in the binary decomposition of the photon number. Our protocol consists of successive, independent measurements of each bit by entangling the ancilla with the cavity, then reading out and resetting the ancilla. Photon loss and ancilla readout errors can flip one or more bits, causing nontrivial errors in the outcome, but these errors have a traceable form which can be captured in a simple hidden Markov model. Relying on the independence of each bit measurement, we mitigate biases in ensembles of measurements, showing good agreement with the predictions of the model. The mitigation improves the average total variation distance error of Fock states from $13.5\%$ to $1.1\%$. We also show that the mitigation is efficiently scalable to an $M$-mode system provided that the errors are independent and sufficiently small. Our work motivates the development of new algorithms that utilize single-shot, high-fidelity PNR detectors.

Direct measurement of the PDC photon statistics by PNR detector

Based on the development of photon-number resolving (PNR) detection system with reliable photon-number resolution of 7 photons, we directly measure the photon-number statistics of the parametric down-conversion (PDC) light generated in a BBO crystal pumped by a continuous coherent laser. Experimental results show the relationship between the PDC photon counts and pump power can be expressed by an exponential growing function. We carry on further investigation on the photon statistics at different pump powers, and comprehensive comparison with the Poisson distribution, thermal distribution, and multi-thermal distribution. After deeply analyzing the correlation coefficient and the Mandle’s Q parameter, we demonstrate that the PDC photons generated in the experiment obey the quasi multi-thermal distribution, one kind of the super Poisson distribution.

Quantum Calibration of Multi-pixel Photon Counter and Its Application in High-Sensitivity Magnetometry With NV Center Ensemble

In recent years, quantum detector tomography (QDT) is widely used in many fields, such as non-Gaussian states preparation, quantum metrology, quantum communication and so forth. In this paper, we used QDT to completely characterize a photon-number-resolving detector (PNRD) based on a multi-pixel photon counter (MPPC) at 650 nm, which operated in continuous wave (CW) mode. Reconstructing the positive operator-valued measure (POVM) accurately by QDT could help us theoretically derived the operation performance of MPPC in quantum sensing with nitrogen-vacancy (NV) center ensemble. The reconstruction fidelity of MPPC is larger than 99.94%, which means that QDT is very reliable. Comparing with conventional silicon avalanche photodiode (Si-APD), the fluorescent contrast of optically detected magnetic resonance (ODMR) spectrum of NV center ensemble detected by MPPC could be significantly improved. Since its excellent linearity and outstanding photon-number-resolving capability, MPPC could be further used in the DC magnetometry of NV center ensemble. We can infer that the magnetic field sensitivity can be effectively improved by replacing Si-APD with MPPC. Reportedly, this is an extremely rare research on the application of MPPC in NV center magnetometry.

Resolving Photon Numbers Using a Superconducting Nanowire with Impedance-Matching Taper.

Time- and number-resolved photon detection is crucial for quantum information processing. Existing photon-number-resolving (PNR) detectors usually suffer from limited timing and dark-count performance or require complex fabrication and operation. Here, we demonstrate a PNR detector at telecommunication wavelengths based on a single superconducting nanowire with an integrated impedance-matching taper. The taper provides a kΩ load impedance to the nanowire, making the detector's output amplitude sensitive to the number of photon-induced hotspots. The prototyping device was able to resolve up to four absorbed photons with 16.1 ps timing jitter and <2 c.p.s. device dark count rate. Its exceptional distinction between single- and two-photon responses is ideal for high-fidelity coincidence counting and allowed us to directly observe bunching of photon pairs from a single output port of a Hong-Ou-Mandel interferometer. This detector architecture may provide a practical solution to applications that require high timing resolution and few-photon discrimination.

Quantum Calibration of Photon-Number-Resolving Detectors Based on Multi-Pixel Photon Counters

In this paper, we reconstructed the positive operator-valued measure (POVM) of a photon-number-resolving detector (PNRD) based on a multi-pixel photon counter (MPPC) by means of quantum detector tomography (QDT) at 791 nm and 523 nm, respectively. MPPC is a kind of spatial-multiplexing PNRD with a silicon avalanche photodiode (Si-APD) array as the photon receiver. Experimentally, the quantum characteristics of MPPC were calibrated at 2 MHz at two different wavelengths. The POVM elements were given by QDT. The fidelity of the reconstructed POVM elements is higher than 99.96%, which testifies that the QDT is reliable to calibrate MPPC at different wavelengths. With QDT and associated Wigner functions, the quantum properties of MPPC can be calibrated more directly and accurately in contrast with those conventional methods of modeling detectors.

Photon-counting and analog operation of a 24-pixel photon number resolving detector based on superconducting nanowires.

We investigate the transition from the photon-counting to the linear operation mode in a large-dynamic range photon-number-resolving-detector (PNRD). A 24-pixel photon-number-resolving-detector, based on superconducting nanowires in a series configuration, has been fabricated and characterized. The voltage pulses, generated by the pixels, are summed up into a single readout pulse whose height is proportional to the detected photon number. The device can resolve up to twenty-five distinct output levels corresponding to the detection of n = 0-24 photons. Due to its large dynamic range, high sensitivity, high speed and wide wavelength range, this device has potential for linear detection in the few tens of photons range. We show its application in the detection of analog optical signals at frequencies up to few hundred MHz and investigate the limits related to the finite number of pixels and to the pixel's dead time.

Measuring quantum correlations using lossy photon-number-resolving detectors with saturation

The variance of difference of photocounts (VDPs) is an established measure of quantum correlations for quantum states of light. It enables us to discriminate between the classical correlation of a two-mode coherent state and the quantum correlation of a twin-beam state. We study the effect of loss and saturation of the photon number-resolving detector on the measurement of the VDPs. An analytic function is derived for this variance, both for the coherent and the twin-beam states. It is found that the VDPs is no longer a reliable entanglement measure in the nonlinear regime of the detector response but it remains useful in some range of values of average photon numbers of the incident light. We also quantify the linear regime of the detector with saturation which will be useful for calibration of the detector quantum efficiency.

Quantum receivers with squeezing and photon-number-resolving detectors forM-ary coherent state discrimination

We propose quantum receivers with optical squeezing and photon-number-resolving detector (PNRD) for the near-optimal discrimination of quaternary phase-shift-keyed coherent state signals. The basic scheme is similar to the previous proposals (e.g. Phys. Rev. A 84, 042328 (2012)) in which displacement operations, on-off detectors, and electrical feedforward operations were used. Here we study two types of receivers where one installs optical squeezings and the other uses PNRDs instead of on-off detectors. We show that both receivers can attain lower error rates than that by the previous scheme and in particular, the PNRD based receiver has a significant gain under the fixed number of feedfoward steps. Moreover, we show that the PNRD based receiver can suppress the errors due to dark counts, which is not possible by the on-off detector based receiver with a limited number of feedforwards.

Modeling the avalanche diode as a photon detector in quantum optical interferometers

Avalanche diodes (ADs) are widely used to count photons in quantum interferometry. In reality they do not count photons, but click once when a bunch of photons arrives in a light pulse. We model this behavior in typical quantum optical interferometers like the Hong-Ou-Mandel beam splitter and the Mach-Zehnder interferometer, and compare it with the behavior of the photon-number-resolving (PNR) detector and the Hanbury-Brown-Twiss detector in these measuring devices. Our results show that quantum interferometric measurements with biphotons could be performed with single ADs, if the noise of the diodes could be reduced. Even a single PNR detector can be used in these interferometers, if the variance of the measurement is determined, since it reveals information about biphoton interference in contrast to the single detector counting rate.

Passive scheme with a photon-number-resolving detector for monitoring the untrusted source in a plug-and-play quantum-key-distribution system

A passive scheme with a beam splitter and a photon-number-resolving (PNR) detector is proposed to verify the photon statistics of an untrusted source in a plug-and-play quantum-key-distribution system by applying a three-intensity decoy-state protocol. The practical issues due to statistical fluctuation and detection noise are analyzed. The simulation results show that the scheme can work efficiently when the total number of optical pulses sent from Alice to Bob is above 10^8, and the dark count rate of the PNR detector is below 0.5 counts/pulse, which is realizable with current techniques. Furthermore, we propose a practical realization of the PNR detector with a variable optical attenuator combined with a threshold detector.

Room temperature photon number resolving detector for infared wavelengths

In this paper we present a photon number resolving detector at infrared wavelengths, operating at room temperature and with a large dynamic range. It is based on the up-conversion of a signal at 1559 nm into visible wavelength and on its detection by a thermoelectrically cooled multi-pixel silicon avalanche photodiodode, also known as a Silicon Photon Multiplier. With the appropriate up-conversion this scheme can be implemented for arbitrary wavelengths above the visible spectral window. The preservation of the poissonian statistics when detecting coherent states is studied and the cross-talk effects on the detected signal can be easily estimated in order to calibrate the detector. This system is well suited for measuring very low intensities at infrared wavelengths and for analyzing multiphoton quantum states.

Highly Sensitive, Photon Number Resolving Detectors Mediated by Phonons Using δ-Doped GaAs Transistors

We report a photon number resolving detector using two-dimensional electron gas (2DEG) based transistors. When the photon pulses impinge on the absorption region, the generated phonons dissipate ballistically in the 2DEG toward the trench isolated nanowire transistors near the surface. The phonon-electron interaction induces a positive conductance in the transistors, resulting in a current increase. With this principle, we obtain an internal quantum efficiency for this type of detector of up to 85%.

Superconducting parallel nanowire detector with photon number resolving functionality

We present a new photon number resolving detector (PNR), the Parallel Nanowire Detector (PND), which uses spatial multiplexing on a subwavelength scale to provide a single electrical output proportional to the photon number. The basic structure of the PND is the parallel connection of several NbN superconducting nanowires (≈100 nm wide, few nm thick), folded in a meander pattern. Electrical and optical equivalents of the device were developed in order to gain insight on its working principle. PNDs were fabricated on 3–4 nm thick NbN films grown on sapphire (substrate temperature T S = 900°C) or MgO (T S = 400°C) substrates by reactive magnetron sputtering in an Ar/N2 gas mixture. The device performance was characterized in terms of speed and sensitivity. The photoresponse shows a full width at half maximum (FWHM) as low as 660 ps. PNDs showed counting performance at 80 MHz repetition rate. Building the histograms of the photoresponse peak, no multiplication noise buildup is observable and a one-photon quantum efficiency can be estimated to be η ∼ 3% (at 700 nm wavelength and 4.2 K temperature). The PND significantly outperforms existing PNR detectors in terms of simplicity, sensitivity, speed, and multiplication noise. †Present address: COBRA Research Institute, Eindhoven University of Technology, Eindhoven, The Netherlands.

Direct measurement of photon number statistics at telecom wavelengths using a charge integration photon detector

In optical quantum information technology, a photon number resolving detector (PNRD) is the basic device for developing photonic quantum computers. The demands for the PNRD are high quantum efficiency and wide dynamic range. We have developed a charge integration photon detector (CIPD) with a quantum efficiency of 80% at telecom wavelengths. The repetition rate of the CIPD is as low as 40 Hz at present, but it can be applied for measurement of short pulses. We report the capability of the CIPD for multiphoton counting over 10 photons, its responsivity to the short pulses, and its high linearity using a binary intensity modulated short pulse (2 ns) train and simultaneous irradiation of two kinds of pulses.