KR-102964028-B1 - TIME DELAY-BASED PHOTON INTERFERENCE DEVICE AND METHOD FOR ENHANCING HONG-OU-MANDEL(HOM) INTERFERENCE BETWEEN PHOTONS WITH FREQUENCY MIXING STATES

KR102964028B1KR 102964028 B1KR102964028 B1KR 102964028B1KR-102964028-B1

Abstract

A time delay-based photon interference device includes a first sequential pulse signal generator that converts a first signal generated through an SPDC process into a first signal in the form of sequential pulses separated in the time domain, a second sequential pulse signal generator that converts a second signal generated through an SPDC process into a second signal in the form of sequential pulses separated in the time domain, and a HOM interferometer that performs simultaneous measurement by interfering the first signal in the form of sequential pulses and the second signal in the form of sequential pulses.

Inventors

임동길
인용섭
조용기
박경득
김동규

Assignees

국방과학연구소

Dates

Publication Date: 20260511
Application Date: 20250910

Claims (17)

A first sequential pulse signal generation unit that, when a first signal in a frequency-mixed state generated through the SPDC process of a first node is input, applies different time delays to a plurality of frequency components included in the first signal to output a first signal in the form of sequential pulses in which the plurality of frequency components are separated in the time domain; A second sequential pulse signal generation unit that, when a second signal in a frequency-mixed state generated through the SPDC process of a second node is input, applies different time delays to a plurality of frequency components included in the second signal to output a second signal in the form of sequential pulses in which the plurality of frequency components are separated in the time domain; and A time-delay-based photon interference device comprising a HOM interferometer that performs simultaneous measurement by interfering a first signal in the form of a sequential pulse and a second signal in the form of a sequential pulse.
In Article 1, The above-mentioned first sequential pulse signal generating unit is, A first demultiplexer that separates a first signal generated through the above SPDC process into multiple spatial modes according to frequency components and outputs it to multiple optical paths; A first time delay unit comprising a plurality of optical paths corresponding to a plurality of spatial modes of the first demultiplexer, and applying different time delays to the plurality of optical paths separated by frequency components; and A time delay-based photon interference device comprising a first multiplexer that combines the plurality of optical paths into a first single path to form a first signal in the form of a sequential pulse.
In Article 2, The above first demultiplexer is a time delay-based photonic interference device that uses a DWDM (Dense Wavelength Division Multiplexer) to separate a first signal generated through the SPDC process into multiple spatial modes according to frequency components.
In Article 2, The above first multiplexer is a time delay-based photonic interference device that combines multiple frequency components with different time delays by combining the plurality of optical paths into the first single path using DWDM to form the first signal in the form of sequential pulses.
In Article 1, The above second sequential pulse signal generating unit is, A second demultiplexer that separates the second signal generated through the above SPDC process into multiple spatial modes according to frequency components and outputs it to multiple optical paths; A second time delay unit comprising a plurality of optical paths corresponding to a plurality of spatial modes of the second demultiplexer, and applying different time delays to the plurality of optical paths separated by frequency components; and A time delay-based photon interference device comprising a second multiplexer that combines the plurality of optical paths into a second single path to form a second signal in the form of a sequential pulse.
In Article 5, The above second demultiplexer is a time delay-based photonic interference device that uses DWDM to separate a second signal generated through the SPDC process into multiple spatial modes according to frequency components.
In Article 5, The above second multiplexer is a time delay-based photonic interference device that combines multiple frequency components with different time delays by combining the plurality of optical paths into the second single path using DWDM to form the second signal in the form of sequential pulses.
A first demultiplexer that outputs a first frequency component of a first signal in a frequency-mixed state generated through the SPDC process of a first node to a first optical path that applies a first time delay, and outputs a second frequency component of the first signal to a second optical path that applies a second time delay different from the first time delay; A first multiplexer that combines a first frequency component of the first signal with a first time delay and a second frequency component of the first signal with a second time delay to form a first signal in the form of sequential pulses in which the first frequency component and the second frequency component are separated in the time domain; and A time delay-based photon interference device comprising a HOM interferometer that performs simultaneous measurement by interfering a first signal in the form of a sequential pulse and a second signal in the form of another sequential pulse, in which the first frequency component and the second frequency component are separated in the time domain.
In Article 8, A second demultiplexer that outputs a first frequency component of a second signal in a frequency-mixed state generated through the SPDC process of a second node to a first optical path that applies a first time delay, and outputs a second frequency component of the second signal to a second optical path that applies a second time delay; and A time delay-based photon interference device further comprising a second multiplexer that combines a first frequency component of the second signal with a first time delay and a second frequency component of the second signal with a second time delay to form a second signal in the form of a sequential pulse in which the first frequency component and the second frequency component are separated in the time domain.
In Article 9, At least one of the first demultiplexer, the first demultiplexer, the second demultiplexer, and the second demultiplexer is a time delay-based photonic interference device using DWDM.
A step in which, when a first sequential pulse signal generator receives a first signal in a frequency-mixed state generated through the SPDC process of a first node, different time delays are applied to a plurality of frequency components included in the first signal to output a first signal in the form of a sequential pulse in which the plurality of frequency components are separated in the time domain; A step in which, when a second signal in a frequency-mixed state generated through the SPDC process of a second node is input to a second sequential pulse signal generator, different time delays are applied to a plurality of frequency components included in the second signal to output a second signal in the form of a sequential pulse in which the plurality of frequency components are separated in the time domain; and A time-delay-based photon interference method comprising the step of performing simultaneous measurement by interfering a first signal in the form of a sequential pulse and a second signal in the form of a sequential pulse using a HOM interferometer.
In Article 11, The step of converting into a first signal in the form of a sequential pulse as described above is: A step of separating the first signal generated through the above SPDC process into multiple spatial modes according to frequency components and outputting it to multiple optical paths; A step of applying different time delays to the plurality of optical paths separated by frequency components; and A time-delay-based photon interference method comprising the step of combining the plurality of optical paths into a first single path to form a first signal in the form of a sequential pulse.
In Article 11, The step of converting into a second signal in the form of a sequential pulse as described above is: A step of separating the second signal generated through the above SPDC process into multiple spatial modes according to frequency components and outputting it to multiple optical paths; A step of applying different time delays to the plurality of optical paths separated by frequency components; and A time-delay-based photon interference method comprising the step of combining the plurality of optical paths into a second single path to form a second signal in the form of a sequential pulse.
In Article 11, A time delay-based photon interference method in which the first sequential pulse signal generator converts a first signal generated through an SPDC process into a first signal in the form of a sequential pulse separated in the time domain, and the second sequential pulse signal generator converts a second signal generated through an SPDC process into a second signal in the form of a sequential pulse separated in the time domain are performed simultaneously.
A step in which a first demultiplexer outputs a first frequency component of a first signal in a frequency-mixed state generated through the SPDC process of a first node to a first optical path that applies a first time delay, and outputs a second frequency component of the first signal to a second optical path that applies a second time delay different from the first time delay; A first multiplexer combines a first frequency component of the first signal to which the first time delay is applied and a second frequency component of the first signal to which the second time delay is applied to form a first signal in the form of a sequential pulse in which the first frequency component and the second frequency component are separated in the time domain; and A time-delay-based photon interference method comprising the step of performing simultaneous measurement by interfering a first signal in the form of a sequential pulse and a second signal in the form of another sequential pulse, in which the first frequency component and the second frequency component are separated in the time domain, with a HOM interferometer.
In Article 15, A step in which a second demultiplexer outputs a first frequency component of a second signal in a frequency-mixed state generated through the SPDC process of a second node to a first optical path that applies a first time delay, and outputs a second frequency component of the second signal to a second optical path that applies a second time delay; and A time delay-based photon interference method further comprising the step of combining a second multiplexer with a first frequency component of the second signal to which a first time delay is applied and a second frequency component of the second signal to which a second time delay is applied to form a second signal in the form of a sequential pulse in which the first frequency component and the second frequency component are separated in the time domain.
In Article 16, A time-delay-based photon interference method in which the step of forming a first signal in the form of a sequential pulse and the step of forming a second signal in the form of a sequential pulse are performed simultaneously.

Description

Time Delay-Based Photon Interference Device and Method for Enhancing Hong-Ou-Mandel (HOM) Interference Between Photons with Frequency Mixing States The present invention relates to a photon interference control technology for improving interference performance between photons having a frequency mixing state generated through a spontaneous parametric down-conversion (SPDC) process, and more specifically, to a time delay-based photon interference device and method for enhancing Hong-Ou-Mandel (HOM) interference between photons having a frequency mixing state. With the advancement of quantum information processing and quantum communication technologies, quantum interference between different photons is garnering attention as a critical technological element. In particular, the implementation of quantum repeaters, which enable long-distance quantum communication, requires high visibility in the quantum interference between independently generated photons. To this end, photon pairs generated through the SPDC process are generally utilized. SPDC is a nonlinear optical process that splits a single high-energy pump photon into two low-energy photons; for convenience, the two generated photons are referred to as the signal photon and the idler photon. These two photons generally exhibit a strong correlation, and frequency correlation is the key issue. If only one photon is observed from a pair of photons with frequency correlation, that state is described as a mixed state on the frequency basis. Interference between photons in a mixed state of frequency results in limited coherence, leading to qualitatively poor quantum interference. For example, let the signal photons among the photon pairs generated by two independent SPDC light sources be designated as the first signal and the second signal, respectively. When attempting HOM interference between the first and second signals, if the photons of the first and second signals are frequency-mixed, the coherence becomes significantly lower. This is because the indistinguishability of the two photons is not guaranteed since the frequency information is mixed completely randomly. Consequently, the result is quantum interference with low coherence. Due to this frequency correlation, the implementation of high-quality interference between independent photons, which is a core element of quantum interference-based technology, is limited, which directly leads to performance degradation in various application technologies such as quantum repeaters, quantum networks, and quantum entanglement swapping. Therefore, a new technical approach is required to improve the coherence of photon pairs with frequency correlation. Although it is possible to generate photon pairs without frequency correlation, this requires using a Type II SPDC process with relatively low nonlinear coefficients or a spectral filter to eliminate frequency correlation; however, both methods cause photon loss, which leads to a problem of lowering the brightness of the light source. FIG. 1 is a block diagram showing a time delay-based photon interference device for enhancing HOM interference between photons having a frequency mixing state according to one embodiment of the present invention. FIG. 2 is a flowchart illustrating a time delay-based photon interference method for enhancing HOM interference between photons having a frequency mixing state according to one embodiment of the present invention. Figure 3 shows an example of the frequency correlation of photon pairs generated through a 0-type SPDC process. FIG. 4 is a block diagram showing a photon interference device according to a comparative example. FIG. 5 is a graph showing the simultaneous measurement results by a time delay-based photon interference device according to one embodiment of the present invention and the simultaneous measurement results by a photon interference device according to a comparative embodiment. Hereinafter, embodiments of the present invention will be described in detail with reference to the attached drawings so that those skilled in the art can easily implement the present invention. The present invention may be embodied in various different forms and is not limited to the embodiments described herein. To clearly explain the present invention, parts unrelated to the explanation have been omitted, and the same reference numerals are used for identical or similar components throughout the specification. Furthermore, throughout the specification, when a part is described as "including" a certain component, this means that, unless specifically stated otherwise, it does not exclude other components but may include additional components. Hereinafter, with reference to FIGS. 1 to 3, a time delay-based photon interference apparatus and method for enhancing HOM interference between photons having a frequency mixing state according to an embodiment of the present invention will be described. FIG. 1 is a block diagram illustrating a time-