CN103048843A - Continuous variable quantum state frequency transformation device - Google Patents

Abstract

A continuous variable quantum state frequency conversion device, including a pumping light source, the laser output from the pumping light source is divided into two beams, and one beam of laser light is coupled with the input continuous variable light field quantum state after passing through a light intensity control system and a beam coupling system in sequence , through the mode matching system and the nonlinear optical resonator to generate the frequency-transformed quantum state, the frequency-transformed quantum state enters the balanced zero-beat measurement system through the beam collimation system and the light field filtering system; the other laser beam output by the pump light source passes through the second After the light intensity control system and the second beam coupling system are coupled with the input local light field, the frequency-transformed local light field is generated through the second mode matching system and the second nonlinear optical resonator, and the frequency-transformed local light field passes through the second beam quasi- The direct system and the second optical field filter system enter the balanced zero-beat measurement system; the device can realize the frequency conversion of the continuous variable quantum state with high efficiency and high fidelity, and is insensitive to the additional noise of the pump light.

Description

Continuous variable quantum state frequency conversion device

technical field

The invention relates to the fields of continuous variable quantum optics and quantum information, in particular to a continuous variable quantum state frequency conversion device.

Background technique

Quantum information networks based on light fields and atomic systems have received great attention and exciting research progress. Due to its extremely fast propagation speed and weak decoherence characteristics, the light field is suitable for long-distance transmission as the carrier of quantum states; and atoms are suitable for the storage of quantum states due to their long coherence time. For future quantum information networks based on light fields and atomic systems, quantum states need to be transferred between different physical carriers with high fidelity. In a real environment, each node of a quantum information network is usually composed of different physical systems, thus having different optical characteristic frequencies. Therefore, quantum interface devices that can realize high-fidelity conversion of optical field quantum states between different optical frequencies will be an important basic component of future quantum information networks. For example, in quantum information networks, quantum states need to be transferred between atomic carriers and optical field carriers; and between optical fields with different carrier wavelengths. By using the frequency conversion technology of the quantum state of the light field, quantum systems with different operating wavelengths can be connected to each other. The orthogonal component of the light field has a continuous spectrum structure, which belongs to the category of continuous variables, and has extremely important applications in the fields of quantum optics and quantum information.

The patent "Conversion of quantum information from one photonic representation to another photonic representation, Patent No.: US 7,449,672 B2" proposes a method and device for frequency conversion of quantum information on photons, but the carrier of quantum information involved in this patent is limited to : photon polarization, photon number, time interval, and angular momentum, excluding the orthogonal component of the light field. The second-order nonlinear optical frequency conversion technology based on optics is one of the most effective schemes to realize the frequency conversion of the continuous variable optical field quantum state. The literature "Observation of quantum frequency conversion, Phys. Rev. Lett. 68, 2153 (1992)" reported that the frequency of one of the non-classical twin beams was converted by the pulse optical sum frequency process, and the frequency converted light was observed experimentally. There is a nonclassical intensity correlation between the field and the remaining beams in the twin beams. In the above experimental scheme, the pump light and the signal light both pass through the nonlinear medium once to interact, so the required pumping light field must be a short pulse light field with high peak power, and for the pumping light field The case of continuous wave light field is not applicable. The literature "Frequency conversion of an entangled state, Phys. Rev. A 73, 033817 (2006)" theoretically analyzes the use of sum-frequency processes to realize the quantum state frequency up-conversion of continuous variable entangled states. This document introduces a resonant cavity, which enhances the nonlinear interaction and is suitable for the frequency conversion of quantum states in the case of continuous waves. The disadvantage is that the resonant cavity resonates with both the input signal light field and the sum-frequency up-conversion light field. Due to the limitation of cavity line width, this scheme is only suitable for narrowband quantum state frequency conversion, which has great limitations. The literature "Frequency conversion of continuous variable quantum states, J.Opt.Soc.Am.B 25,269(2008)" theoretically analyzes the frequency conversion of the broadband continuous wave continuous variable quantum state based on the resonant cavity, and studies the effect of the additional fluctuation noise of the pump light on However, this literature does not propose how to effectively overcome the adverse effects of the additional fluctuation noise of the pump light. In practice, the laser light source as a strong pump light usually has large additional fluctuation noise, which will greatly affect and reduce the fidelity of the frequency conversion of the continuous variable light field quantum state.

Contents of the invention

The object of the present invention is to provide a continuous variable quantum state frequency conversion device with compact structure and good stability. The device can realize high-efficiency and high-fidelity frequency up-conversion or down-conversion of the quantum state of the continuous variable light field, and the fidelity of the frequency conversion of the quantum state is insensitive to the extra fluctuation noise of the pumping light field.

A continuous variable quantum state frequency conversion device provided by the present invention includes a pumping light source, first and second light intensity control systems, first and second beam coupling systems, first and second mode matching systems, first and second light intensity control systems, The second nonlinear optical resonator, the first and second beam collimation systems, the first and second light field filtering systems, and the balanced zero-beat measurement system; a beam of laser light output by the pumping light source passes through the first light successively After the strong control system and the first beam coupling system are coupled with the input continuous variable light field quantum state, the frequency conversion quantum state is generated through the first mode matching system and the first nonlinear optical resonator, and the frequency conversion quantum state is passed through the first beam quasi The direct system and the first light field filter system enter the balanced zero-beat measurement system; the other laser beam output by the pump light source passes through the second light intensity control system and the second beam coupling system in sequence, and then is coupled with the input local light field, and passes through the first The second mode matching system and the second nonlinear optical resonator generate a frequency-transformed local light field, and the frequency-transformed local light field enters the balanced zero-beat measurement system through the second beam collimation system and the second light field filter system;

The pumping light source is a single-frequency continuous wave laser light source;

Both the first nonlinear optical resonator and the second nonlinear optical resonator are composed of a nonlinear medium, a cavity length locking system and at least two mirrors, one of which is fixed on a piezoelectric ceramic as an input coupling The outer surface of the reflector is coated with an anti-reflection film for pump light and signal light, and the inner surface is coated with a high-transmission film for signal light, a partial reflection film for pump light, and a high-transmission film for frequency conversion light; as an output coupling The inner surface of the mirror is coated with a high-transparency film for signal light, a high-reflection film for pump light, and a high-transmission film for frequency-converted light, and the outer surface is coated with an anti-reflection film for signal light and frequency-converted light; the rest of the mirrors are The inner surface is coated with high reflection film for signal light, pump light and frequency conversion light; the two surfaces of the nonlinear medium are coated with antireflection film for signal light, pump light and frequency conversion light.

Both the first light field filter system and the second light field filter system have at least one plane that can achieve high transmission of frequency conversion light and high reflection of pump light, signal light and the second harmonic of pump light Mirror composition.

The first beam coupling system and the second beam coupling system are both composed of a 45-degree flat mirror coated on both sides, wherein the incident surface corresponding to the pump light is coated with a 45-degree pump light antireflection film, and the incident surface corresponding to the signal light The surface is coated with a 45-degree high-reflection film for signal light and a high-transmission film for pump light.

In the device of the present invention, the first light intensity control system and the second light intensity control system are used to precisely control the light intensity of the pump light to achieve the best quantum state frequency conversion; the first beam coupling system and the second beam coupling system are used to Coupling pump light and signal light, so that the path space of the two light beams completely coincides; the first mode matching system and the second mode matching system are used to realize the spatial mode of pump light and signal light to the first nonlinear optical resonator and the second The mode matching of two nonlinear optical resonators; the first nonlinear optical resonator and the second nonlinear optical resonator are used to realize the efficient and high-fidelity quantum state frequency conversion of the signal light field and the frequency conversion of the local light field; the first The beam collimating system and the second beam collimating system are used to collimate the divergent light fields emitted by the first nonlinear optical resonator and the second nonlinear optical resonator; the first optical field filtering system and the second optical field filtering The system is used to completely filter out the remaining pump light, signal light and the second harmonic light field of the pump light in the output light fields of the first beam collimation system and the second beam collimation system, and only allow the frequency conversion light field Lossless pass-through; balanced zero-beat measurement system is used to detect the quadrature component information of the quantum state of the frequency-transformed light field.

Compared with prior art, advantage and effect of the present invention:

The continuous variable quantum state frequency conversion device of the present invention, after the signal light continuous variable quantum state and the corresponding local light field is incident on the device, can realize the frequency conversion of the continuous variable quantum state and the balance zero of the frequency conversion quantum state with high efficiency and high fidelity At the same time, the device is insensitive to the additional fluctuation noise of the pump light field.

The continuous variable quantum state frequency conversion device of the present invention can realize the frequency conversion of the local light field while obtaining the frequency conversion of the light quantum state of the signal, effectively solving the problem of the local light field required for the balanced zero-beat measurement of the frequency conversion quantum state.

In the continuous variable quantum state frequency conversion device of the present invention, the pump light source in the frequency conversion process of the signal light quantum state and the local light field comes from the same laser, so that the extra fluctuation noise of the pump light source will be transferred to the frequency conversion light field and the corresponding local light field at the same time. In the light field, since the balanced zero-beat measurement is only related to the relative phase of the local light field and the signal light field, the extra fluctuation phase noise from the common pump light source will be offset, so the device can effectively overcome the extra phase of the pump light field Detrimental effects of noise on the frequency transformation process of continuous variable quantum states.

Description of drawings

Figure 1 Schematic diagram of continuous variable quantum state frequency conversion device

Figure 2 The noise power spectrum of the quantum state of the input signal light field, A is the noise power spectrum of the quadrature amplitude component, B is the noise power spectrum of the quadrature phase component

Figure 3 The noise power spectrum of the quantum state of the frequency-transformed light field, A is the noise power spectrum of the quadrature amplitude component, B is the noise power spectrum of the quadrature phase component

Detailed ways

A continuous variable quantum state frequency conversion device, as shown in Figure 1: including a pump light source 1, a first light intensity control system 2, a first beam coupling system 3, a first mode matching system 4, a first nonlinear optical resonance 5, the first beam collimation system 6, the first light field filter system 7, the second light intensity control system 8, the second beam coupling system 9, the second mode matching system 10, the second nonlinear optical resonator 11, The second beam collimation system 12, the second optical field filtering system 13 and the balance zero-beat measurement system 14; the pump light source 1 adopts a 1550 nm single-frequency continuous wave fiber laser, and its output laser is divided into two parts, wherein one beam of laser light is sequentially After passing through the first light intensity control system 2 and the first beam coupling system 3, it is coupled with the input 532 nm continuous variable coherent state light field S, and then passes through the first mode matching system 4 and the first nonlinear optical resonator 5 to generate 810 nm The frequency-transformed quantum state, the frequency-transformed quantum state enters the balanced zero-beat measurement system 14 through the first beam collimation system 6 and the first light field filter system 7; the other laser beam output by the pump light source 1 passes through the second light intensity control system in turn After the system 8 and the second beam coupling system 9 are coupled with the input 532 nm local light field L, the 810 nm frequency conversion local light field is generated through the second mode matching system 10 and the second nonlinear optical resonator 11, and the frequency conversion local light field The field enters the balance zero-beat measurement system 14 through the second light beam collimation system 12 and the second light field filter system 13; the 810 nanometer frequency conversion quantum state is measured through the balance zero-beat measurement system 14; the first light intensity control system 2 and the second The two light intensity control systems 8 are composed of a half-wave plate and a polarizing beam splitting prism; the first beam coupling system 3 and the second beam coupling system 9 are composed of two-sided coated flat mirrors, and the pump light incident surface is coated with 1550 nm S-polarized 45-degree anti-reflection film, the signal light incident surface is coated with 532nm S-polarized 45-degree high-reflection film and 1550nm S-polarized 45-degree high-transmission film; the first nonlinear optical resonator 5 and the second nonlinear optical resonator The resonant cavity of 11 is composed of two mirror standing wave cavities, the outer surface of the input coupling mirror is coated with 532, 1550 nanometer anti-reflection coating, and the inner surface of the input coupling mirror is coated with 532, 810 nanometer high-transparency film and 1550 nanometer part Reflective film, the inner surface of the output coupling mirror is coated with 532, 810 nm high-transparency film and 1550 nm high-reflection film, the outer surface of the output coupling mirror is coated with 810, 532 nm high-transparency film, the two channels of the nonlinear crystal The optical end surface is coated with anti-reflection coatings for 532, 1550 and 810 nanometer lasers, and the error electrical signal of the cavity length locking system is fed back to the piezoelectric ceramics on the mirror to realize the cavity length of the nonlinear optical resonator and the resonance of the pump light; Both the first light field filter system 7 and the second light field filter system 13 are composed of three double-sided coated flat filters, wherein the front surface of the first filter plate is coated with a 810 nm high-transparency film and a 532 nm high-reflection film , the back surface is coated with 810nm anti-reflection film, the front surface of the second filter is coated with 810nm high-transmission film and 1550nm high-reflection film, the rear surface Coated with 810nm anti-reflection coating, the front surface of the third filter is coated with 810nm high-transparency coating and 775nm high-reflection coating, and the rear surface is coated with 810nm anti-reflection coating.

Fig. 2 is the experimentally measured fluctuation noise power spectrum (normalized to the corresponding standard quantum limit noise) of the quadrature amplitude component and quadrature phase component of the 532 nm coherent state signal light field incident on the device of the present invention. It can be seen that when the analysis frequency is greater than 6MHz, the fluctuation noise of the orthogonal amplitude component and the orthogonal phase component of the 532nm signal light field coincides with the corresponding standard quantum limit noise, which is a coherent state.

Fig. 3 is the fluctuating noise power spectrum of the quadrature amplitude component and quadrature phase component of the frequency-transformed 810 nanometer light field quantum state output by the device of the present invention. It can be seen that when the analysis frequency is greater than 6MHz, the fluctuation noise of the quadrature amplitude component and quadrature phase component of the 810nm signal light field coincides with the corresponding standard quantum limit noise, which is a coherent state. The average photon-to-photon conversion efficiency of the corresponding 532nm signal light field to the 810nm frequency conversion light field is measured in the experiment as 86%. Therefore, the device of the invention can realize efficient and high-fidelity frequency conversion from a coherent state at 532 nanometers to a coherent state at 810 nanometers. At the same time, in the process of frequency conversion, the 1550nm light field as the pump light has classical fluctuation noise far greater than the standard quantum limit at the analysis frequency of 2MHz-20MHz (when the measurement power is about 8 mW, the corresponding noise is high 10dB-20dB above the standard quantum noise limit), thus confirming that the device of the present invention is not sensitive to the additional fluctuation noise of the pump light field.

Claims (3)

1. continuous variable quantum state frequency-transposition arrangement, it is characterized in that, comprise pump light source (1), the beam of laser of pump light source (1) output is successively through being coupled with the continuous variable optical state S that inputs after the first intensity control system (2) and the first light beam coupling system (3), produce frequency transformation quantum attitude through first mode matching system (4) and the first nonlinear optics resonator (5), frequency transformation quantum attitude enters balance homodyne detection system (14) through the first passing through a collimating system (6) and the first light field filtering system (7); Another Shu Jiguang of pump light source (1) output is successively through being coupled with the local light field L that inputs after the second intensity control system (8) and the second light beam coupling system (9), produce the local light field of frequency transformation through the second pattern matching system (10) and the second nonlinear optics resonator (11), the local light field of frequency transformation enters balance homodyne detection system (14) through the second passing through a collimating system (12) and the second light field filtering system (13);

Described pump light source (1) is the single-frequency continuous wave LASER Light Source;

Described the first nonlinear optics resonator (5) and the second nonlinear optics resonator (11) consist of by nonlinear medium, the long locking system in chamber and two catoptrons at least, one of them catoptron is fixed on the piezoelectric ceramics, be coated with antireflective film to pump light and flashlight as the catoptron outside surface of input coupling, inside surface is coated with the high transmittance film of flashlight, the part reflectance coating of pump light and the high transmittance film of frequency inverted light; Catoptron inside surface as the output coupling is coated with the high transmittance film to flashlight, the highly reflecting films of pump light and the high transmittance film of frequency inverted light, and outside surface is coated with the antireflective film to flashlight and frequency inverted light; Remaining catoptron inside surface is coated with the highly reflecting films to flashlight, pump light and frequency inverted light; Two surfaces of nonlinear medium are coated with the antireflective film to flashlight, pump light and frequency inverted light.

2. a kind of continuous variable quantum state frequency-transposition arrangement as claimed in claim 1, it is characterized in that, described the first light beam coupling system (3) and the second light beam coupling system (9) consist of by 45 degree plane mirrors of two sides plated film, the plane of incidence that wherein pump light is corresponding is coated with 45 degree pump light antireflective films, and the plane of incidence that flashlight is corresponding is coated with the high transmittance film of 45 degree flashlight highly reflecting films and pump light.

3. a kind of continuous variable quantum state frequency-transposition arrangement as claimed in claim 1, it is characterized in that, described the first light field filtering system (7) and the second light field filtering system (13) be by realizing the high transmission of frequency inverted light, and at least one plane mirror of the high reflection of second harmonic of pump light, flashlight and pump light is consisted of.

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