Planar series arrays of up to 500 proximity effect superconducting bridges have been fabricated with sufficient uniformity to respond coherently to incident radiation (10-20,000MHz) without separate biasing. By varying the geometry, resistance for the arrays can range from .1-50Ω. Despite this high total impedance, low frequency coherent response to external radiation is limited only by single bridge voltage noise. Low frequency (30-500MHz) coherent internal voltage oscillations of current biased arrays have been detected and confirm that the oscillating voltage signal grows linearly in bridge number while the voltage noise increases only as the square root. An array of n elements responds to incident high frequency radiation in first approximation as though it were a simple Josephson junction but quantized in units of n(h/2e). Coincident operation to high frequency depends strongly on small (\leq 1\mu) bridge separation. High resistance, coincident operation, and exponential dependence of critical current on temperature make these arrays good candidates for voltage standards, coherent and bolometric radiation detectors, and cryogenic rf sources.Planar series arrays of up to 500 proximity effect superconducting bridges have been fabricated with sufficient uniformity to respond coherently to incident radiation (10-20,000MHz) without separate biasing. By varying the geometry, resistance for the arrays can range from .1-50Ω. Despite this high total impedance, low frequency coherent response to external radiation is limited only by single bridge voltage noise. Low frequency (30-500MHz) coherent internal voltage oscillations of current biased arrays have been detected and confirm that the oscillating voltage signal grows linearly in bridge number while the voltage noise increases only as the square root. An array of n elements responds to incident high frequency radiation in first approximation as though it were a simple Josephson junction but quantized in units of n(h/2e). Coincident operation to high frequency depends strongly on small (\leq 1\mu) bridge separation. High resistance, coincident operation, and exponential dependence of critical current on temperature make these arrays good candidates for voltage standards, coherent and bolometric radiation detectors, and cryogenic rf sources.

IEEE Transactions on MagneticsMar 1, 197526 citations

A nonlinear theory of laser noise and coherence. II

Hermann Haken

The European Physical Journal AAug 1, 196547 citations

The Interaction of Coherent Radiation with Matter

Zoltan Fried, Lloyd C. Kannenberg

Springer eBooksJan 1, 19841 citation

Second-order coherence of microwave photons emitted by a quantum point contact

Fabian Hassler, Daniel Otten

Shot noise of electrons that are transmitted with probability $T$ through a quantum point contact (biased at a voltage ${V}_{0}$ ) leads to a fluctuating current that in turn emits radiation in the microwave regime. By calculating the Fano factor $F$ for the case where only a single channel contributes to the transport, it has been shown that the radiation produced at finite frequency ${\ensuremath{\omega}}_{0}$ close to $e{V}_{0}/\ensuremath{\hbar}$ and at low temperatures is nonclassical with sub-Poissonian statistics ( $F<1$ ). The origin of this effect is the fermionic nature of the electrons producing the radiation, which reduces the probability of simultaneous emission of two or more photons. However, the Fano factor, being a time-averaged quantity, offers only limited information about the system. Here, we calculate the second-order coherence ${g}^{(2)}(\ensuremath{\tau})$ for this source of radiation. We show that due to the interference of two contributions, two photon processes (leading to bunching) are completely absent at zero temperature for $T=50\phantom{\rule{0.16em}{0ex}}%$ . At low temperatures, we find a competition of the contribution due to Gaussian current-current fluctuations (leading to bunching) with the one due to non-Gaussian fluctuations (leading to antibunching). At slightly elevated temperatures, the non-Gaussian contribution becomes suppressed, whereas the Gaussian contributions remain largely independent of temperature. We show that the competition of the two contributions leads to a nonmonotonic behavior of the second-order coherence as a function of time. As a result, ${g}^{(2)}(\ensuremath{\tau})$ obtains a minimal value for times ${\ensuremath{\tau}}^{*}\ensuremath{\simeq}{\ensuremath{\omega}}_{0}^{\ensuremath{-}1}$. Close to this time, the second-order coherence remains below 1 at temperatures where the Fano factor is already above 1. We identify realistic experimental parameters that can be used to test the sub-Poissonian nature of the radiation.Shot noise of electrons that are transmitted with probability $T$ through a quantum point contact (biased at a voltage ${V}_{0}$) leads to a fluctuating current that in turn emits radiation in the microwave regime. By calculating the Fano factor $F$ for the case where only a single channel contributes to the transport, it has been shown that the radiation produced at finite frequency ${\ensuremath{\omega}}_{0}$ close to $e{V}_{0}/\ensuremath{\hbar}$ and at low temperatures is nonclassical with sub-Poissonian statistics ($F<1$). The origin of this effect is the fermionic nature of the electrons producing the radiation, which reduces the probability of simultaneous emission of two or more photons. However, the Fano factor, being a time-averaged quantity, offers only limited information about the system. Here, we calculate the second-order coherence ${g}^{(2)}(\ensuremath{\tau})$ for this source of radiation. We show that due to the interference of two contributions, two photon processes (leading to bunching) are completely absent at zero temperature for $T=50\phantom{\rule{0.16em}{0ex}}%$. At low temperatures, we find a competition of the contribution due to Gaussian current-current fluctuations (leading to bunching) with the one due to non-Gaussian fluctuations (leading to antibunching). At slightly elevated temperatures, the non-Gaussian contribution becomes suppressed, whereas the Gaussian contributions remain largely independent of temperature. We show that the competition of the two contributions leads to a nonmonotonic behavior of the second-order coherence as a function of time. As a result, ${g}^{(2)}(\ensuremath{\tau})$ obtains a minimal value for times ${\ensuremath{\tau}}^{*}\ensuremath{\simeq}{\ensuremath{\omega}}_{0}^{\ensuremath{-}1}$. Close to this time, the second-order coherence remains below 1 at temperatures where the Fano factor is already above 1. We identify realistic experimental parameters that can be used to test the sub-Poissonian nature of the radiation.

arXiv:1509.00485Physical Review BNov 16, 201513 citations

Amplification of Coherent Radiation

Karl Friedrich Renk

Graduate texts in physicsNov 21, 20111 citation

Quantum limitations on the detection of coherent and incoherent signals

Carl W. Helstrom

In order to discover what effect the quantum nature of radiation has on the detection of signals at optical frequencies, the detectability of coherent and, in the threshold limit, incoherent signals is calculated on the basis of an idealized quantum-mechanical model of a receiver. The detectabilities reduce at low frequencies to those found by ordinary signal-detection theory; at high frequencies they depend on Planck's constant. For incoherent signals of high frequency the threshold detector is equivalent to a system that focuses the radiation on a photoelectric surface of unit quantum efficiency and optimally processes the emitted electrons.In order to discover what effect the quantum nature of radiation has on the detection of signals at optical frequencies, the detectability of coherent and, in the threshold limit, incoherent signals is calculated on the basis of an idealized quantum-mechanical model of a receiver. The detectabilities reduce at low frequencies to those found by ordinary signal-detection theory; at high frequencies they depend on Planck's constant. For incoherent signals of high frequency the threshold detector is equivalent to a system that focuses the radiation on a photoelectric surface of unit quantum efficiency and optimally processes the emitted electrons.

IEEE Transactions on Information TheoryOct 1, 196515 citations

Shot noise of electrons that are transmitted with probability

T

through a quantum point contact (biased at a voltage

{V}_{0}

) leads to a fluctuating current that in turn emits radiation in the microwave regime. By calculating the Fano factor

F

for the case where only a single channel contributes to the transport, it has been shown that the radiation produced at finite frequency ${\ensuremath{\omega}}_{0}$ close to $e{V}_{0}/\ensuremath{\hbar}$ and at low temperatures is nonclassical with sub-Poissonian statistics (

F<1

). The origin of this effect is the fermionic nature of the electrons producing the radiation, which reduces the probability of simultaneous emission of two or more photons. However, the Fano factor, being a time-averaged quantity, offers only limited information about the system. Here, we calculate the second-order coherence ${g}^{(2)}(\ensuremath{\tau})$ for this source of radiation. We show that due to the interference of two contributions, two photon processes (leading to bunching) are completely absent at zero temperature for

T=50\phantom{\rule{0.16em}{0ex}}%

. At low temperatures, we find a competition of the contribution due to Gaussian current-current fluctuations (leading to bunching) with the one due to non-Gaussian fluctuations (leading to antibunching). At slightly elevated temperatures, the non-Gaussian contribution becomes suppressed, whereas the Gaussian contributions remain largely independent of temperature. We show that the competition of the two contributions leads to a nonmonotonic behavior of the second-order coherence as a function of time. As a result, ${g}^{(2)}(\ensuremath{\tau})$ obtains a minimal value for times ${\ensuremath{\tau}}^{*}\ensuremath{\simeq}{\ensuremath{\omega}}_{0}^{\ensuremath{-}1}$. Close to this time, the second-order coherence remains below 1 at temperatures where the Fano factor is already above 1. We identify realistic experimental parameters that can be used to test the sub-Poissonian nature of the radiation.