CN209930215U - Quantum parametric amplifier - Google Patents
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- CN209930215U CN209930215U CN201920907681.8U CN201920907681U CN209930215U CN 209930215 U CN209930215 U CN 209930215U CN 201920907681 U CN201920907681 U CN 201920907681U CN 209930215 U CN209930215 U CN 209930215U
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Abstract
The utility model discloses a quantum parameter amplifier, which comprises a capacitor module, a reflection type microwave resonant cavity and a superconductive quantum interference device of an adjustable inductor which are connected in sequence and used for forming a vibration amplifying circuit, wherein one end of the superconductive quantum interference device, which is far away from the reflection type microwave resonant cavity, is grounded; and the accessible adjusts the inductance of the superconductive quantum interference device of adjustable inductance and makes the resonant frequency of reflective microwave resonant cavity equal to the frequency of treating the amplified signal, treats that the amplified signal gets into the oscillation amplification circuit from capacitance module department coupling, and the oscillation amplification circuit is enlargied under pumping signal's effect and is treated the amplified signal to produce a plurality of kinds of idle frequency signals, still include the second microwave resonant cavity, connect the one end of keeping away from capacitance module at reflective microwave resonant cavity, the resonant frequency of second microwave resonant cavity equals with the frequency of one of them kind of idle frequency signal, the utility model discloses the pumping signal frequency that quantum parameter amplifier is in best mode need not to select for the doubling of waiting to amplify the signal frequency.
Description
Technical Field
The utility model belongs to the signal amplifier field, especially a quantum parameter amplifier.
Background
In the field of quantum computing, in order to obtain an operation result of a quantum chip, a signal output by the quantum chip, that is, a qubit read signal, needs to be collected and analyzed, the qubit read signal is usually very weak, a multi-stage amplifier needs to be added to an output line of the qubit read signal to improve signal strength, and a quantum parametric amplifier is usually used as a preceding stage amplifier. When a quantum parametric amplifier is operated, the accompanying noise is as low as a level close to the quantum limit, which is the origin of its name.
The existing quantum parametric amplifier works based on a nonlinear frequency mixing principle, and in order to effectively amplify a qubit read signal, a pumping signal with a frequency close to the frequency of a signal to be amplified or a frequency doubling of the signal needs to be additionally applied when the quantum parametric amplifier works in an optimal mode, for example, a four-wave frequency mixing working mode corresponds to the applied pumping signal close to the signal to be amplified, and a three-wave frequency mixing working mode corresponds to the applied pumping signal close to twice the frequency of the signal to be amplified.
In summary, in the conventional quantum parametric amplifier, in an optimal operating mode, that is, the frequency of the pump signal must be selected as a multiple of the frequency of the signal to be amplified, there exist irrelevant signals with frequencies extremely close to the frequency of the signal to be amplified in the output signal, and these irrelevant signals are difficult to be eliminated by the filter because the frequencies are too close to the signal to be amplified, and they interfere with the demodulation process of the qubit reading signal, so that the demodulation fidelity and demodulation efficiency of the quantum chip operation result are greatly reduced.
SUMMERY OF THE UTILITY MODEL
The utility model aims at providing a quantum parametric amplifier to solve not enough among the prior art, make quantum parametric amplifier be in the pumping signal's of best mode frequency need not to select for the doubling of frequency of waiting to amplify the signal frequency.
The utility model adopts the technical scheme as follows:
a quantum parametric amplifier comprises a capacitance module, a reflection type microwave resonant cavity and a superconducting quantum interference device with adjustable inductance which are sequentially connected and used for forming an oscillation amplification circuit; one end of the superconducting quantum interference device of the adjustable inductor, which is far away from the reflective microwave resonant cavity, is grounded; and the resonance frequency of the reflective microwave resonant cavity can be made equal to the frequency of the signal to be amplified by adjusting the inductance of the superconducting quantum interference device of the adjustable inductance, wherein: the signal to be amplified is coupled from the capacitance module and enters the oscillation amplifying circuit, and the oscillation amplifying circuit amplifies the signal to be amplified under the action of a pumping signal and generates a plurality of idle frequency signals;
the quantum parametric amplifier further comprises a second microwave resonant cavity connected to one end of the reflective microwave resonant cavity far away from the capacitor module, wherein: the resonant frequency of the second microwave resonant cavity is equal to the frequency of one of the idlers.
Furthermore, the superconducting quantum interference device of the adjustable inductor comprises a superconducting quantum interferometer and a magnetic flux modulation circuit which are connected in mutual inductance coupling;
the superconducting quantum interferometer is a closed-loop device formed by connecting a plurality of Josephson junctions in parallel;
the magnetic flux modulation circuit is used for adjusting the magnetic flux of the closed loop device so as to adjust the inductance of the superconducting quantum interferometer.
Further, the superconducting quantum interferometer is a closed-loop device formed by connecting two Josephson junctions in parallel.
Further, the magnetic flux modulation circuit comprises a magnetic flux modulation line and a current device for generating bias current which are connected in sequence;
wherein: the flux modulation lines are used for transmitting the bias current and enabling the bias current to be mutually inductively coupled with the superconducting quantum interferometer.
Further, the magnetic flux modulation line is a coplanar waveguide microstrip transmission line.
Further, the current device is a current source, or a voltage source and a resistor which are connected in sequence and can provide the bias current.
Further, a pumping signal for amplifying the signal to be amplified is coupled into the oscillation amplifying circuit from the capacitance module or the magnetic flux modulating circuit.
Further, the capacitor module is one of an interdigital capacitor, a distributed capacitor and a parallel capacitor.
Furthermore, the reflective microwave resonant cavity is a coplanar waveguide microwave resonant cavity with the length of one quarter of the wavelength of the signal to be amplified.
Furthermore, the quantum parametric amplifier also comprises a voltage modulation circuit;
the voltage modulation circuit is arranged at one end, close to the reflective microwave resonant cavity, of the superconducting quantum interference device of the adjustable inductor;
the superconducting quantum interferometer device with the adjustable inductance can release an idler signal which is generated in the oscillation amplifying circuit and has the same resonant frequency as the second microwave resonant cavity under the action of the bias voltage provided by the voltage modulation circuit.
Furthermore, one end of the second microwave resonant cavity far away from the reflective microwave resonant cavity is grounded.
Further, the quantum parametric amplifier further comprises a circulator;
the circulator is arranged at one end of the capacitance module, which is far away from the reflective microwave resonant cavity, and is used for inputting the signal to be amplified into the oscillation amplifying circuit and outputting an output signal generated by the oscillation amplifying circuit.
Further, the quantum parametric amplifier further comprises a filter;
the filter is arranged at one end of the circulator far away from the capacitor module.
Compared with the prior art, the utility model provides a quantum parametric amplifier, which comprises a capacitance module, a reflection type microwave resonant cavity and a superconducting quantum interference device with adjustable inductance which are connected in sequence and used for forming an oscillation amplifying circuit; one end of the superconducting quantum interference device of the adjustable inductor, which is far away from the reflective microwave resonant cavity, is grounded; the frequency of the reflective microwave resonant cavity is equal to the frequency of a signal to be amplified by adjusting the inductance of the superconducting quantum interference device of the adjustable inductance, so that the signal to be amplified and a pumping signal perform nonlinear interaction in the reflective microwave resonant cavityFurther amplifying the signal to be amplified, and after the signal to be amplified and the pumping signal are subjected to nonlinear interaction, the output signal not only comprises the signal to be amplified, but also comprises various idlers fiSetting the resonant frequency of the second microwave resonant cavity to be equal to one of the idler frequencies, passively converting part of energy of the pumping signal into one of the idler frequencies equal to the resonant frequency of the second microwave resonant cavity, and enabling the pumping signal frequency f of the quantum parametric amplifier to be in the optimal working mode at the momentpNeed not be selected as the signal f to be amplifiedsSo that each idler f is output when the selected pump signal frequency is at a distance from the signal frequency to be amplified that can be split by a filteriAre also all related to the signal f to be amplifiedsHave the distance that can be by the wave filter split, the utility model discloses a set up second microwave resonant cavity, make partial energy of pumping signal can turn into the idler that equals with second microwave resonant cavity resonant frequency, when the resonant frequency of selecting suitable second microwave resonant cavity, the pumping signal is selected to the resonant frequency through this second microwave resonant cavity again, can make to produce an idler release that equals with second microwave resonant cavity resonant frequency in the quantum parameter amplifier, and except that this other all irrelevant signals of the idler that is released all can with treat that the amplified signal keeps the distance that can be by the wave filter split on the frequency spectrum, and then can eliminate these irrelevant signals, improve quantum parameter amplifier to the reading fidelity of quantum bit reading signal.
Drawings
Fig. 1 is a schematic structural diagram of a quantum parametric amplifier provided by an embodiment of the present invention;
fig. 2 is a schematic circuit diagram of a quantum parametric amplifier according to an embodiment of the present invention;
fig. 3 is a schematic circuit diagram of a quantum parametric amplifier according to another embodiment of the present invention.
Detailed Description
The embodiments described below by referring to the drawings are exemplary only for explaining the present invention, and should not be construed as limiting the present invention.
Referring to fig. 1, an embodiment of the present invention provides a quantum parametric amplifier, which includes a capacitance module 100, a reflective microwave cavity 200 and a superconducting quantum interference device 400 of an adjustable inductor, which are connected in sequence, for forming an oscillation amplifying circuit; one end of the superconducting quantum interference device 400 of the adjustable inductor, which is far away from the reflective microwave resonant cavity 200, is grounded; and the resonance frequency of the reflective microwave resonant cavity 200 can be made equal to the frequency of the signal to be amplified by adjusting the inductance of the superconducting quantum interference device 400 of the adjustable inductance, wherein: the signal to be amplified is coupled from the capacitance module 100 into the oscillation amplifying circuit, and the oscillation amplifying circuit amplifies the signal to be amplified under the action of the pumping signal and generates a plurality of idle frequency signals; the quantum parametric amplifier further includes a second microwave resonant cavity 300, the second microwave resonant cavity 300 is connected to one end of the reflective microwave resonant cavity 200 away from the capacitor module 100, and a resonant frequency of the second microwave resonant cavity 300 is equal to a frequency of one of the idlers.
Compared with the prior art, the utility model provides a quantum parametric amplifier, which comprises a capacitance module 100, a reflection type microwave resonant cavity 200, a second microwave resonant cavity 300 and a superconductive quantum interference device 400 of an adjustable inductor which are connected in sequence and used for forming an oscillation amplifying circuit; one end of the superconducting quantum interference device 400 of the adjustable inductor, which is far away from the reflective microwave resonant cavity 200, is grounded; the inductance of the inductance-adjustable superconducting quantum interference device 400 is adjusted to make the resonant working frequency of the reflective microwave resonant cavity 200 equal to the frequency of the signal to be amplified, so that the signal to be amplified and the pumping signal perform nonlinear interaction in the reflective microwave resonant cavity 200 to further amplify the signal to be amplified, and after the signal to be amplified and the pumping signal perform nonlinear interaction, the output signal not only includes the signal to be amplified, but also includes various idle frequency signals fiThe resonant frequency of the second microwave cavity 300 is set to a frequency equal to one of the idler frequencies, while causing the quantum to resonatePump signal frequency f of a parametric amplifier in an optimal operating modepNeed not be selected as the signal f to be amplifiedsSo that each idler f is output when the selected pump signal frequency is at a distance from the signal frequency to be amplified that can be split by a filteriAre also all related to the signal f to be amplifiedsHave the distance that can be by the wave filter split, the utility model discloses a set up second microwave resonant cavity 300 for the partial energy of pump signal can turn into with an idler that second microwave resonant cavity 300 resonant frequency equals when selecting the resonant frequency of suitable second microwave resonant cavity, the rethread pump signal is selected to the resonant frequency of second microwave resonant cavity 300, can make produce in the quantum parametric amplifier with an idler release that second microwave resonant cavity 300 resonant frequency equals, and all other irrelevant signals except this idlers released all can with treat that the amplified signal keeps the distance that can be by the wave filter split on the frequency spectrum, and then can eliminate these irrelevant signals, improve quantum parametric amplifier to the reading fidelity of qubit read signal.
In the field of quantum computing, in order to obtain an operation result of a quantum chip, a qubit read signal, which is a signal output by the quantum chip, needs to be collected and analyzed, and the qubit read detection signal is very weak. Taking the superconducting qubit system as an example, the qubit reading detection signal is usually in the frequency band of 4-8GHz, and the power is as low as-140 dBm or less, even as low as-150 dBm. Considering the coupling efficiency of the qubit detection signal to the qubit reading detector, a power of-150 dBm to-140 dBm corresponds to a photon count inside the detector of about 1-10. Such weak detection signals are additionally lost after being transmitted again through the detector. Therefore, one of the core problems to be solved in the application of quantum chips is how to extract effective quantum state information from such weak qubit reading signals.
Assuming that the qubit read signal that finally leaves the qubit read detector has 10 valid photons, they will enter the subsequent line, with heatNoise, electrical noise, etc. are mixed together. Where the standard thermal noise satisfies the thermodynamic distribution, it can be used
Converted into a photon number n, k in the above formulaBBoltzmann constant, T ambient noise temperature at frequency f, h planckian constant. Assuming that the quantum chip is in a temperature environment of 10mK, n is less than 0.1 and can be ignored according to the above formula. However, the receiving system of the qubit reading signal is at room temperature, n is about 1000, and if the qubit reading signal is directly transmitted out, it will be buried in noise. Therefore, the use of a parametric amplifier is necessary.
Any amplifier will additionally introduce noise while amplifying the original signal. We usually measure the equivalent temperature of the noise, i.e. the noise, and the larger the index, the worse the noise. The amplifier must deteriorate the signal-to-noise ratio and therefore the amplifier should be set to raise the gain of the amplifier as much as possible while controlling the noise temperature of the amplifier.
Noise temperature is also satisfied
Thus, we can translate the noise temperature into the number of noise photons at frequency f. Whereas the signal-to-noise ratio can be described as the ratio of the number of signal photons to the number of noise photons.
The amplifier which is commercially available at present has the best performance, and is a low noise amplifier produced by the Swedish LNF company, and can amplify signals in a 4-8GHz frequency band, and the noise temperature is about 3K. In this measure, the number of noise photons is about 10, so the maximum achievable signal-to-noise ratio using commercial amplifiers is about 1, and the best quantum parametric amplifiers can achieve the noise level of the standard quantum limit, i.e., n is 0.5. Generally, n fluctuates within 0.5-2. Therefore, the signal-to-noise ratio of the system can be improved by about 5-20 times by using the quantum parameter amplifier.
Although the quantum parameter amplifier solves the problem of extracting effective quantum state information from such a weak qubit reading signal by greatly improving the signal-to-noise ratio, a new problem is brought. The existing quantum parametric amplifier works based on a nonlinear frequency mixing principle, and in order to effectively amplify a qubit read signal, a pumping signal with a frequency close to the frequency of a signal to be amplified or a frequency doubling of the signal needs to be additionally applied when the quantum parametric amplifier works in an optimal mode, for example, a four-wave frequency mixing working mode corresponds to the applied pumping signal close to the signal to be amplified, and a three-wave frequency mixing working mode corresponds to the applied pumping signal close to twice the frequency of the signal to be amplified.
Inputting a signal f to be amplified during the operation of the quantum parametric amplifiersAnd a pump signal fpSignal f to be amplifiedsAt the pump signal fpAmplifying under the action of the first and second amplifiers to output signals to be amplified, and simultaneously, based on the nonlinear frequency mixing principle, the output signals also comprise frequency-doubled pumping signals nfpHalf-frequency pump signal 1/2fpAnd various idlers fiSignal f to be amplifiedsPump signal fpAnd an idler fiWill satisfy the formula: mf (m) ofs+nfi＝lfpWherein: m, n and l are integers, and when m, n and l take different values, different idlers f are obtainedi. When the quantum parametric amplifier is in the four-wave mixing modepFrequency selection close to the signal f to be amplifiedsOf the output signal, the pump signal fpAnd 2f in the idlerp-fs、2fs-fpBecause of the proximity of the signal f to be amplifiedsAffecting the acquisition of the signal to be amplified; when the quantum parametric amplifier is in a three-wave mixing mode of operation, the pumping signal fpFrequency selection is close to 2 times of signal f to be amplifiedsOf the output signal, half-frequency pump signal 1/2fpAnd f in the idlerp-fsBecause of the proximity of the signal f to be amplifiedsAffecting the acquisition of the signal to be amplified.
Specifically, referring to fig. 1 and fig. 2, a quantum parametric amplifier according to an embodiment of the present invention is provided, where the quantum parametric amplifier includes a capacitor module 100, a reflective microwave resonant cavity 200, a second microwave resonant cavity 300 and a superconducting quantum interference device 400 of an adjustable inductor, which are connected in sequence, where the capacitor module 100, the reflective microwave resonant cavity 200, and the superconducting quantum interference device 400 of the adjustable inductor are connected to ground at one end and the other end, which are far away from the capacitor module 100, of the reflective microwave resonant cavity 200; and the inductance of the superconducting quantum interference device 400 of the adjustable inductance can be adjusted to make the frequency of the reflective microwave resonant cavity 200 equal to the frequency of the signal to be amplified, wherein: the signal to be amplified is coupled from the capacitance module 100 into the oscillation amplifying circuit, and the oscillation amplifying circuit amplifies the signal to be amplified under the action of the pumping signal and generates a plurality of idle frequency signals;
it should be noted that each of the idlers satisfies the following formula:
mfs+nfi＝lfp
wherein: m, n, l are integers, fsFor the frequency, f, of the signal to be amplifiedpFor the frequency, f, of the pumping signaliThe resonant frequency of the second microwave cavity 300 is equal to the frequency of one of the idlers, it should be noted that the above formula is based on the nonlinear mixing principle, and when the signal f to be amplified issAnd a pump signal fpWhen determined, m, n and l take different values, and various idlers f are obtainedi。
Wherein, the capacitance module 100 is used for coupling the signal to be amplified into the reflective microwave resonant cavity 200, and it should be noted that, generally, the microwave resonant cavity must be connected with an external circuit to form a microwave system to work, and must be excited by the microwave signal in the external circuit to establish oscillation in the cavity, and the oscillation in the cavity must be output to an external load through coupling, and generally, the capacitance module is adopted to establish coupling with the microwave resonant cavity, and the capacitance module 100 in this embodiment can select interdigital capacitance, distributed capacitance or parallel capacitance, and the utility model discloses do not limit to the concrete form of the capacitance module 100.
It should be noted that the oscillation amplification circuit is a common structure in the field of signal amplification and is a key component of many electronic devices, and the oscillation amplification circuit is usually represented as an LC oscillation circuit, including interconnected capacitors and inductors, which can be used for generating signals of specific frequencies as well as separating signals of specific frequencies from more complex signals. In the field of quantum computing, in order to obtain an operation result of a quantum chip, a signal output by the quantum chip, namely a qubit read signal, needs to be collected and analyzed, the qubit read signal is usually very weak and needs to be amplified, because the qubit read signal belongs to a high-frequency signal and has a very short wavelength, and because a lumped LC oscillating circuit uses a capacitive-inductive device with a large structural size and the energy of the LC oscillating circuit is dispersedly distributed in a surrounding space, the dissipation speed is very high, we must use a quantum parametric amplifier used in the quantum field.
Generally, a quantum parametric amplifier includes a capacitor, a microwave resonant cavity, a superconducting quantum interferometer and a magnetic flux bias adjusting circuit for modulating the superconducting quantum interferometer, which are connected in sequence, wherein one end of the superconducting quantum interferometer far away from the resonant cavity is grounded, and the basic principle is as follows: the alternating current generated in the superconducting quantum interferometer is utilized to form an inductor which forms an LC oscillation circuit with a capacitor, so that a single-mode optical field is constructed in the microwave resonant cavity, a weak signal to be amplified and a pumping signal enter a device together, the signal to be amplified in the microwave resonant cavity is amplified, and meanwhile, the whole process is in a superconducting state and almost has no dissipation.
Wherein: it should be noted that the superconducting quantum interferometer is a closed-loop device formed by connecting several josephson junctions in parallel, wherein: josephson junctions are generally formed by sandwiching two superconductors with a thin barrier layer, such as the S (superconductor) -I (semiconductor or insulator) -S (superconductor) structure, SIS for short, in which superconducting electrons can tunnel through a semiconductor or insulator from one side of one of the superconductors to the superconductor on the other side, or josephson effect, and the resulting current is called josephson current, which forms a josephson interferometer, or superconducting quantum interferometer, when several josephson junctions are connected together to form a closed loop device.
It should be noted that, the utility model discloses a work flow is as follows, through adjusting the inductance of the superconductive quantum interferometer 400 of adjustable inductance, makes the resonance frequency of work of reflection-type microwave cavity 200 is unanimous with the frequency of treating the amplified signal, thereby makes the signal of treating to amplify be in resonance amplification effect is the best in reflection-type microwave cavity 200, will treat that amplified signal and pump signal couple into in reflection-type microwave cavity 200, treat that amplified signal will amplify under the effect of pump signal, it is required to explain not only including amplifying signal in the output signal, still includes pump signal, half frequency pump signal, doubling of frequency pump signal and various idlers, set up the resonance frequency of second microwave cavity 300 to equal with one of them idler frequency, when the resonance frequency of selecting suitable second microwave cavity 300 is f2Then according to the relation mfs+nf2＝lfpSelecting a suitable pumping frequency fpThe pumping frequency f can be obtained by making m-n-l-1pGenerated in the oscillation amplifying circuit and f2The idlers with equal frequencies will flow out through the second microwave cavity 300 and the superconducting quantum interferometer device 400 to ground.
It should be noted that the utility model discloses quantum parameter amplifier need design various parameters before the work, one of the final objectives of the utility model is that make all can not treat among the irrelevant signal of output and enlarge the signal and cause the interference, even also they can be by the wave filter split, provide a specific example here, when treating to enlarge the signal frequency and be 4GHz, at first can design one of them idler and be 2GHz, confirm according to this idler the resonant frequency f of second microwave cavity 3002Is 2GHz by the relation mfs+nf2＝lfpLet m-n-l-1 select the appropriate pumping frequency fpIs 6Ghz, then according to the formula mfs+nfi＝lfpConsidering other possible idlers, it can be shown that when m, n and l take different values, the resulting idler fiWill not treat the amplified signal fsCausing interference. The following table givesWhen the frequency of the signal to be amplified is 4GHz and the frequency of the pumping signal is 6GHz, the signal f to be amplified is generateds8 idlers f with the closest frequencyi。
Table 1: 8 kinds of idle frequency signals fi
| m | 1 | 1 | 1 | 1 | -1 | -1 | -1 | -1 |
| l | 1 | 1 | -1 | -1 | 1 | 1 | -1 | -1 |
| n | 1 | -1 | 1 | -1 | 1 | -1 | 1 | -1 |
| fi | 2GHz | 10GHz | -10Ghz | -2GHz | -2GHz | 10GHz | -10GHz | 2GHz |
From the above table, the signal f to be amplified is generateds8 idlers f with the closest frequencyiAre all in accordance with the signal f to be amplifiedsKept at a distance, then other idlers f are generatediWill not treat the amplified signal fsCausing interference.
The traditional quantum parametric amplifier has another problem that when an actual quantum chip works, a large number of quantum bit signals need to be read out simultaneously, quantum state information of each quantum bit is carried and transmitted by an independent signal, and the frequency of the quantum state information carrying signal is different from the frequency of quantum state information carrying signals of other quantum bits. Reading multiple qubits simultaneously means that multiple signals to be amplified carrying information need to pass through a quantum parameter amplifier. Each of which produces a plurality of extraneous signals while obtaining an amplification effect, and at least one of which is close to the signal to be amplified. In addition, an extraneous signal generated from a signal to be amplified is likely to be additionally close to the frequency of another signal to be amplified.
Specifically, for example: input of a signal f to be amplified of a conventional quantum parametric amplifiersRespectively having a frequency of 6.4GHz and 6.58GHz (0.18 GHz apart, filter separable), a conventional quantum parametric amplifier pump signal fpCan be designed to be 6.5GHz corresponding to a four-wave mixing mode of operation, then according to the formula mfs+nfi＝lfpAmplified signal f of 6.4GHzsOne of the idlers fiAt 6.6GHz, the 6.58GHz signal will be affected (at 0.02GHz distance, it is difficult to split).
When the quantum parametric amplifier of the present invention is adopted, the resonant frequency f of the second microwave resonant cavity 300 is determined according to an idler, for example, 4GHz2At 4GHz, according to the 4GHz signal and the 6.4GHz amplified signal fsDesigning the pump signal fpAt 5.2GHz, it can be seen that the 5.2GHz pump signal fpAmplified signal f corresponding to 6.4GHz and 6.58GHz respectivelysMixing the signals to obtain all idlers fiAmplified signal f equal to both 6.4GHz and 6.58GHzsKeeping a detachable distance.
The superconducting quantum interference device 400 of the adjustable inductor comprises a superconducting quantum interferometer 410 and a magnetic flux modulation circuit 420 which are connected in a mutual inductance coupling manner, and particularly, refer to fig. 2; the superconducting quantum interferometer 410 is a closed-loop device formed by connecting a plurality of Josephson junctions in parallel; the flux modulation circuit 420 is used to adjust the inductance of the superconducting quantum interferometer 410 by adjusting the magnetic flux of the closed loop device.
The magnetic flux modulation circuit 420 comprises a magnetic flux modulation line and a current device for generating a bias current which are connected in sequence; wherein: the flux modulation lines are used to carry the bias current and to mutually inductively couple the bias current to the superconducting quantum interferometer 410.
It should be noted that, the current device for generating the bias current may be a current source, or a voltage source and a resistor which are connected in sequence and can provide the bias current, and the present invention is not limited to the specific form of the current source.
Further, the reflective microwave resonant cavity 200 is a coplanar waveguide microwave resonant cavity with a length of one fourth of the wavelength of the signal to be amplified, and a coplanar waveguide microwave resonant cavity with a length of one fourth of the wavelength of the signal to be amplified is adopted, because the strongest electric field of the coplanar waveguide microwave resonant cavity with a length of one fourth of the wavelength of the signal to be amplified is located at one end close to the capacitor module 100, the weakest electric field is located at one end close to the superconducting quantum interference device 300, and the output signal is output from one end close to the strongest signal coupling position, i.e., close to the capacitor module 100.
It should be noted that when the resonant frequency of the second microwave cavity 300 is different from the resonant frequency of the reflective microwave cavity 200, an idler at the resonance of the second microwave cavity 300 that is the same as the resonant frequency of the second microwave cavity will not enter the reflective microwave cavity 200.
In the microwave field, the coplanar waveguide is three parallel metal thin film conducting strip layers prepared on the surface of a dielectric layer, wherein the conducting strip layer positioned in the center is used for transmitting microwave signals, the conducting strip layers on two sides are connected to a ground plane, the biggest difference with the general circuit is that the coplanar waveguide is a distributed circuit element, the capacitance/inductance/reactance/impedance of the distributed circuit element is uniformly distributed along the signal propagation direction of the coplanar waveguide, the coplanar waveguide propagates TEM waves, and the impedance of the waveguide is equal everywhere along the signal propagation direction, so that no signal reflection exists, and signals can almost pass without loss; in addition, coplanar waveguides have no cutoff frequency, while common lumped circuits have cutoff frequencies. For a section of uniform coplanar waveguide, most microwave signals in the frequency range can be transmitted smoothly, and the section of uniform coplanar waveguide is called a transmission line, namely a coplanar waveguide transmission line. When the designed coplanar waveguide transmission line has a certain length, and a capacitance node is respectively constructed at two ends of the coplanar waveguide transmission line, the microwave signal is reflected after encountering the node, resonance is formed in the section of transmission line, and a resonant cavity is formed.
Preferably, the flux modulation line for transmitting the bias current may also use a coplanar waveguide transmission line.
Preferably, an end of the second microwave cavity 300 away from the reflective microwave cavity 200 is grounded, and the arrangement is such that an idler generated by the second microwave cavity 300 can also flow out through the ground.
Further, referring to fig. 3, since the amplified signal to be amplified is to be output from the side of the reflective microwave cavity 200 close to the capacitor module 100 via the capacitor module 100, in order to isolate the input signal to be amplified from the output signal, the quantum parametric amplifier further includes a circulator 500, and the circulator 500 is disposed at an end of the capacitor module 100 away from the reflective microwave cavity 200.
Further, referring to fig. 3, in order to filter out extraneous signals other than the amplified signal in the output signal, the signal output terminal of the circulator 500 is further provided with a filter 600, wherein the extraneous signals mainly refer to a pump signal, a half-frequency pump signal, a frequency-doubled pump signal, and various idlers.
Further, the quantum parametric amplifier further comprises a voltage modulation circuit 700; the voltage modulation circuit 700 is disposed at one end of the superconducting quantum interference device 400 of the adjustable inductor, which is close to the reflective microwave resonant cavity 200; the superconducting quantum interferometer device 300 with adjustable inductance can release one of the idlers generated in the oscillation amplifying circuit under the action of the bias voltage provided by the voltage modulation circuit 700.
It should be noted that, when a voltage bias is applied to two ends of the superconducting quantum interferometer, the current passing through the josephson junction is an alternating oscillating superconducting current, and the oscillation frequency (or josephson frequency) will be proportional to the bias voltage, which makes the josephson junction have the ability to radiate or absorb electromagnetic waves, and it satisfies the following relation:
2eV＝hf
wherein: h is the Planck constant.
Since the superconducting quantum interferometer device composed of several josephson junctions connected in parallel has the ability to absorb electromagnetic waves, when a voltage bias is applied to the superconducting quantum interferometer device 400 with adjustable inductance, the pair of current couperots on the josephson junctions tunnels energy absorbing microwave signals out through the josephson junctions to the ground, when the voltage bias is properly selected, so that f in the relation 2eV ═ hf is equal to the frequency of one of the idlers generated by the oscillation amplifying circuit, and the idler generated in the oscillation amplifying circuit is completely absorbed and appears as the idler is released.
It should be noted that, when the applied bias voltage makes the frequency of the idler released by the superconducting quantum interferometer apparatus 400 with adjustable inductance equal to the resonant frequency of the second microwave cavity 300, the ability of converting part of the energy of the pump signal into the idler equal to the resonant frequency of the second microwave cavity is actively strengthened, and since the voltage modulation circuit 700 is connected at the position where the electric field of the reflective microwave cavity 200 is the weakest, the dc voltage bias output by the voltage modulation circuit 700 hardly affects the microwave signal in the reflective microwave cavity 200.
It should be noted that, the conventional quantum parametric amplifier can achieve the maximum amplification effect only when the frequency of the pump signal is equal to an integral multiple of the frequency of the signal to be amplified. And under the corresponding three-wave mixing working mode, the frequency of the pumping signal is equal to the frequency of the signal to be amplified. In the four-wave mixing mode of operation, the frequency of the pump signal is equal to twice the frequency of the signal to be amplified. In the three-wave mixing mode, the pump signal and the amplified signal in the output signal are not well distinguished. In the four-wave mixing mode, the half-frequency pump signal and the amplified signal in the output signal are not well distinguished. Adopt the utility model relates to a quantum parameter amplifier, make the pumping signal frequency that quantum parameter amplifier is in best mode need not to select for the doubling of frequency of waiting to amplify the signal this moment, when the resonant frequency and the pumping signal of selecting suitable second microwave resonant cavity, can make each kind of irrelevant signal that produces in the quantum parameter amplifier all can keep the distance that can be by the wave filter split on the frequency spectrum with waiting to amplify the signal, and then can adopt the convenient these irrelevant signals of elimination of back level wave filter, improve quantum parameter amplifier to the reading fidelity of quantum bit reading signal.
The structure, features and effects of the present invention have been described in detail above according to the embodiment shown in the drawings, and the above description is only the preferred embodiment of the present invention, but the present invention is not limited to the implementation scope shown in the drawings, and all changes made according to the idea of the present invention or equivalent embodiments modified to the same changes should be considered within the protection scope of the present invention when not exceeding the spirit covered by the description and drawings.
Claims (13)
1. A quantum parametric amplifier, comprising: the quantum parametric amplifier includes:
the superconducting quantum interference device comprises a capacitance module, a reflection type microwave resonant cavity and an adjustable inductor which are sequentially connected and used for forming an oscillation amplifying circuit; one end of the superconducting quantum interference device of the adjustable inductor, which is far away from the reflective microwave resonant cavity, is grounded;
the resonance frequency of the reflective microwave resonator can be made equal to the frequency of the signal to be amplified by adjusting the inductance of the superconducting quantum interference device of the adjustable inductance, wherein: the signal to be amplified is coupled from the capacitance module and enters the oscillation amplifying circuit, the oscillation amplifying circuit amplifies the signal to be amplified under the action of a pumping signal and generates a plurality of idle frequency signals, the quantum parametric amplifier further comprises a second microwave resonant cavity, and the second microwave resonant cavity is connected to one end, far away from the capacitance module, of the reflection type microwave resonant cavity, wherein: the resonant frequency of the second microwave resonant cavity is equal to the frequency of one of the idlers.
2. The quantum parametric amplifier of claim 1, wherein the tunable-inductor superconducting quantum interference device comprises a mutual inductance coupling connected superconducting quantum interferometer and a flux modulation circuit;
the superconducting quantum interferometer is a closed-loop device formed by connecting a plurality of Josephson junctions in parallel;
the magnetic flux modulation circuit is used for adjusting the magnetic flux of the closed loop device so as to adjust the inductance of the superconducting quantum interferometer.
3. A quantum parametric amplifier according to claim 2, wherein the superconducting quantum interferometer is a closed loop device consisting of two josephson junctions connected in parallel.
4. A quantum parametric amplifier according to claim 2, wherein the flux modulating circuit comprises a flux modulating line and a current device for generating a bias current connected in series;
wherein: the flux modulation lines are used for transmitting the bias current and enabling the bias current to be mutually inductively coupled with the superconducting quantum interferometer.
5. A quantum parametric amplifier according to claim 4, wherein the flux modulation line is a coplanar waveguide microstrip transmission line.
6. A quantum parametric amplifier according to claim 4, wherein the current device is a current source or a voltage source and a resistor connected in series to provide the bias current.
7. A quantum parametric amplifier according to claim 2, wherein a pump signal for amplifying the signal to be amplified is coupled from the capacitance module or the flux modulation circuit into the oscillation amplification circuit.
8. A quantum parametric amplifier according to claim 1, wherein the capacitance module is one of an interdigital capacitor, a distributed capacitor, and a parallel capacitor.
9. A quantum parametric amplifier according to claim 1, wherein the reflective microwave cavity is a coplanar waveguide microwave cavity with a length of one quarter of the wavelength of the signal to be amplified.
10. A quantum parametric amplifier according to claim 1, further comprising a voltage modulation circuit;
the voltage modulation circuit is arranged at one end, close to the reflective microwave resonant cavity, of the superconducting quantum interference device of the adjustable inductor;
the superconducting quantum interferometer device with the adjustable inductance can release an idler signal which is generated in the oscillation amplifying circuit and has the same resonant frequency as the second microwave resonant cavity under the action of the bias voltage provided by the voltage modulation circuit.
11. A quantum parametric amplifier according to claim 1, wherein an end of the second microwave cavity remote from the reflective microwave cavity is grounded.
12. A quantum parametric amplifier according to any of claims 1-11, further comprising a circulator;
the circulator is arranged at one end of the capacitance module, which is far away from the reflective microwave resonant cavity, and is used for inputting the signal to be amplified into the oscillation amplifying circuit and outputting an output signal generated by the oscillation amplifying circuit.
13. A quantum parametric amplifier according to claim 12, further comprising a filter;
the filter is arranged at one end of the circulator far away from the capacitor module.
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| CN201920907681.8U CN209930215U (en) | 2019-06-17 | 2019-06-17 | Quantum parametric amplifier |
| PCT/CN2020/080478 WO2020253292A1 (en) | 2019-06-17 | 2020-03-20 | Quantum parameter amplifier |
| US17/057,286 US11894818B2 (en) | 2019-06-17 | 2020-03-20 | Quantum parameter amplifier |
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| CN201920907681.8U CN209930215U (en) | 2019-06-17 | 2019-06-17 | Quantum parametric amplifier |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110120792A (en) * | 2019-06-17 | 2019-08-13 | 合肥本源量子计算科技有限责任公司 | A kind of quantum parameters amplifier |
| CN112272046A (en) * | 2020-10-29 | 2021-01-26 | 清华大学 | Signal forwarding device |
| CN114362691A (en) * | 2022-03-17 | 2022-04-15 | 壹甲子(成都)通讯有限公司 | AC small signal driving information pick-up circuit |
-
2019
- 2019-06-17 CN CN201920907681.8U patent/CN209930215U/en active Active
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110120792A (en) * | 2019-06-17 | 2019-08-13 | 合肥本源量子计算科技有限责任公司 | A kind of quantum parameters amplifier |
| CN112272046A (en) * | 2020-10-29 | 2021-01-26 | 清华大学 | Signal forwarding device |
| CN114362691A (en) * | 2022-03-17 | 2022-04-15 | 壹甲子(成都)通讯有限公司 | AC small signal driving information pick-up circuit |
| CN114362691B (en) * | 2022-03-17 | 2022-05-24 | 壹甲子(成都)通讯有限公司 | AC small signal driving information pick-up circuit |
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