CN110120792A - A kind of quantum parameters amplifier - Google Patents

A kind of quantum parameters amplifier Download PDF

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Publication number
CN110120792A
CN110120792A CN201910522955.6A CN201910522955A CN110120792A CN 110120792 A CN110120792 A CN 110120792A CN 201910522955 A CN201910522955 A CN 201910522955A CN 110120792 A CN110120792 A CN 110120792A
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signal
quantum
frequency
amplified
reflection type
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孔伟成
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Hefei Native Quantum Computing Technology Co Ltd
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Hefei Native Quantum Computing Technology Co Ltd
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Priority to CN201910522955.6A priority Critical patent/CN110120792A/en
Publication of CN110120792A publication Critical patent/CN110120792A/en
Priority to US17/057,286 priority patent/US11894818B2/en
Priority to PCT/CN2020/080478 priority patent/WO2020253292A1/en
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    • HELECTRICITY
    • H03ELECTRONIC CIRCUITRY
    • H03FAMPLIFIERS
    • H03F7/00Parametric amplifiers
    • H03F7/02Parametric amplifiers using variable-inductance element; using variable-permeability element
    • HELECTRICITY
    • H03ELECTRONIC CIRCUITRY
    • H03FAMPLIFIERS
    • H03F7/00Parametric amplifiers
    • H03F7/04Parametric amplifiers using variable-capacitance element; using variable-permittivity element

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Microwave Amplifiers (AREA)

Abstract

The invention discloses a kind of quantum parameters amplifiers, quantum parameters amplifier includes the superconducting quantum interference device of the sequentially connected capacitance module for forming oscillator-amplification circuit, reflection type microwave resonant cavity and controllable impedance, and superconducting quantum interference device is grounded far from one end of reflection type microwave resonant cavity;And the resonance frequency of reflection type microwave resonant cavity can be made to be equal to frequency signal to be amplified by adjusting the inductance of the superconducting quantum interference device of controllable impedance, it is signal to be amplified that oscillator-amplification circuit is coupled into from capacitance module, oscillator-amplification circuit amplifies signal to be amplified under the action of pump signal, and generate several idler, it further include the second microwave cavity, it is connected to the one end of reflection type microwave resonant cavity far from capacitance module, the resonance frequency of second microwave cavity is equal with one of frequency of idler, the frequency that quantum parameters amplifier of the present invention is in the pump signal of optimum working mode is not necessarily to be selected as the frequency multiplication of frequency signal to be amplified.

Description

A kind of quantum parameters amplifier
Technical field
The invention belongs to signal amplifier field, especially a kind of quantum parameters amplifier.
Background technique
In quantum calculation field, the operation result of quantum chip in order to obtain, it would be desirable to the output of quantum chip Signal, that is, quantum bit reads signal and is acquired and analyzes, and usual quantum bit reading signal is very faint, generally requires Quantum bit is read in the outlet line of signal plus casacade multi-amplifier is to improve signal strength, in general, the amplifier of prime is adopted With quantum parameter amplifier.When quantum parameters amplifier operation, down to the level close to quantum limit, this is exactly subsidiary noise The origin of its title.
Existing quantum parameter amplifier is worked based on non-linear frequency mixing principle, in order to which quantum bit is effectively read signal Amplify so that quantum parameters amplifier operation optimal mode need it is additional apply frequency and frequency signal to be amplified or The close pump signal of its frequency multiplication, for example, the corresponding pump signal applied close to it is signal to be amplified it is corresponding be that four-wave mixing works Mode, it is three wave mixing operating mode that the pump signal of application is corresponding close to twice of frequency signal to be amplified.
To sum up, under optimum working mode, i.e. the frequency of pump signal must be chosen to existing quantum parameters amplifier The frequency multiplication of frequency signal to be amplified, there are frequencies in the signal of output extremely close to the irrelevant signal of frequency signal to be amplified, For these irrelevant signals since frequency gets too close to signal to be amplified to being difficult to eliminate by filter, they can interfere quantum ratio Spy reads the demodulating process of signal, and the demodulation fidelity of quantum chip operation result is caused to be greatly reduced with demodulation efficiency.
Summary of the invention
The object of the present invention is to provide a kind of quantum parameters amplifiers, to solve deficiency in the prior art, so that quantum The frequency that parameter amplifier is in the pump signal of optimum working mode is not necessarily to be selected as the frequency multiplication of frequency signal to be amplified.
The technical solution adopted by the invention is as follows:
A kind of quantum parameters amplifier, quantum parameters amplifier include sequentially connected for forming oscillator-amplification circuit The superconducting quantum interference device of capacitance module, reflection type microwave resonant cavity and controllable impedance;The Superconducting Quantum of the controllable impedance Interference device is grounded far from one end of the reflection type microwave resonant cavity;And the Superconducting Quantum of the adjusting controllable impedance can be passed through The inductance of interference device makes the resonance frequency of the reflection type microwave resonant cavity be equal to frequency signal to be amplified, in which: described Signal to be amplified that the oscillator-amplification circuit is coupled into from the capacitance module, the oscillator-amplification circuit is in pump signal Under the action of amplify described signal to be amplified, and generate several idler;
The quantum parameters amplifier further includes the second microwave cavity, and second microwave cavity is connected to described anti- Penetrate the one end of type micro-wave resonant cavity far from the capacitance module, in which: the resonance frequency of second microwave cavity with wherein A kind of frequency of the idler is equal.
Further, the superconducting quantum interference device of the controllable impedance includes the superconductive quantum interference of Mutual Inductance Coupling connection Instrument and Flux modulation circuit;
The superconducting quantum interference device (SQUID) is the closed-loop device being made of several Josephson junction parallel connections;
The Flux modulation circuit is used to adjust the Superconducting Quantum by the magnetic flux for adjusting the closed-loop device The inductance of interferometer.
Further, the superconducting quantum interference device (SQUID) is the closed-loop device being made of two Josephson junction parallel connections.
Further, the Flux modulation circuit includes sequentially connected Flux modulation line and for generating bias current Current device;
Wherein: the Flux modulation line is used for transmission the bias current, and makes the bias current and the superconduction amount Sub- interferometer Mutual Inductance Coupling.
Further, the Flux modulation line is co-planar waveguide microstrip transmission line.
Further, the current device is current source or sequentially connected can provide the voltage of the bias current Source and resistance.
Further, for amplifying the pump signal signal to be amplified from the capacitance module or the magnetic flux tune Circuit processed is coupled into the oscillator-amplification circuit.
Further, the capacitance module is that interdigital capacitor, distributed capacitor and run-in index capacitor are one of.
Further, it is the coplanar of the wavelength a quarter signal to be amplified that the reflection type microwave resonant cavity, which is length, Waveguide microwave resonant cavity.
Further, the quantum parameters amplifier further includes voltage modulation circuit;
The superconducting quantum interference device that the controllable impedance is arranged in the voltage modulation circuit declines close to the reflection Wave resonance chamber one end;
The superconducting quantum interference device (SQUID) device of the controllable impedance can be in the bias voltage that the voltage modulation circuit provides The idler equal with the resonance frequency of second microwave cavity that will be generated in the oscillator-amplification circuit under effect Release.
Further, second microwave cavity is grounded far from one end of the reflection type microwave resonant cavity.
Further, the quantum parameters amplifier further includes circulator;
The one end of the capacitance module far from the reflection type microwave resonant cavity is arranged in the circulator, and being used for will be described The input oscillator-amplification circuit signal to be amplified, and the output signal that the oscillator-amplification circuit is generated exports.
Further, the quantum parameters amplifier further includes filter;
The one end of the circulator far from the capacitance module is arranged in the filter.
Compared with prior art, the present invention provides a kind of quantum parameters amplifier, including it is sequentially connected for forming The superconducting quantum interference device of the capacitance module of oscillator-amplification circuit, reflection type microwave resonant cavity and controllable impedance;It is described adjustable The superconducting quantum interference device of inductance is grounded far from one end of the reflection type microwave resonant cavity;It further include the second microwave resonance Chamber is connected to the described one end of reflection type microwave resonant cavity far from capacitance module, by the superconduction amount for adjusting the controllable impedance The inductance of sub- interference device makes the frequency of the reflection type microwave resonant cavity be equal to frequency signal to be amplified, so as to Amplified signal and pump signal carried out in reflection type microwave resonant cavity nonlinear interaction so that amplify it is signal to be amplified, to After amplified signal and pump signal carry out nonlinear interaction, includes not only signal to be amplified in output signal, further include each Kind idler fi, set equal with one of idler frequency for the resonance frequency of second microwave cavity The portion of energy of frequency, pump signal will passively be converted into one kind equal with the resonance frequency of second microwave cavity Idler makes quantum parameters amplifier be in the pump signal frequency f of optimum working mode at this timepWithout being selected as wait put Big signal fsFrequency multiplication, thus when selection pump signal frequency and frequency signal to be amplified have can by filter split away from From when, each idler f of outputiAlso all with f signal to be amplifiedsWith the distance that can be split by filter, the present invention is logical The second microwave cavity of setting is crossed, the portion of energy of pump signal is converted into and the second microwave cavity resonance frequency A kind of equal idler when the resonance frequency for selecting suitable second microwave cavity, then passes through second microwave resonance The resonance frequency of chamber selects pump signal, can to generate in quantum parameters amplifier and the second microwave cavity resonance frequency A kind of equal idler release of rate, and in addition to other all irrelevant signals of the idler being released can be with The distance signal to be amplified for keeping to be split by filter on frequency spectrum, and then these irrelevant signals can be eliminated, improve quantum Parameter amplifier reads the reading fidelity of signal to quantum bit.
Detailed description of the invention
Fig. 1 is a kind of structural schematic diagram of quantum parameters amplifier provided in an embodiment of the present invention;
Fig. 2 is a kind of circuit diagram of quantum parameters amplifier provided in an embodiment of the present invention;
Fig. 3 is a kind of circuit diagram for quantum parameters amplifier that another embodiment of the invention provides.
Specific embodiment
The embodiments described below with reference to the accompanying drawings are exemplary, for explaining only the invention, and cannot be construed to Limitation of the present invention.
Referring to Fig. 1, the embodiment provides a kind of quantum parameters amplifier, the quantum parameters amplifier includes It is sequentially connected for forming the super of the capacitance module 100 of oscillator-amplification circuit, reflection type microwave resonant cavity 200 and controllable impedance Lead quantum interference device 400;The superconducting quantum interference device 400 of the controllable impedance is far from the reflection type microwave resonant cavity 200 one end ground connection;And it can be made by the inductance of the superconducting quantum interference device 400 of the adjusting controllable impedance described reflective The resonance frequency of microwave cavity 200 is equal to frequency signal to be amplified, in which: described signal to be amplified from the capacitance module The oscillator-amplification circuit is coupled at 100, the oscillator-amplification circuit amplifies described wait put under the action of pump signal Big signal, and generate several idler;The quantum parameters amplifier further includes the second microwave cavity 300, and described Two microwave cavities 300 are connected to the one end of the reflection type microwave resonant cavity 200 far from the capacitance module 100, and described The resonance frequency of two microwave cavities 300 is equal with the frequency of one of idler.
Compared with prior art, the present invention provides a kind of quantum parameters amplifier, including it is sequentially connected for forming The capacitance module 100 of oscillator-amplification circuit, reflection type microwave resonant cavity 200, the second microwave cavity 300 and controllable impedance it is super Lead quantum interference device 400;The superconducting quantum interference device 400 of the controllable impedance is far from the reflection type microwave resonant cavity 200 one end ground connection;Inductance by adjusting the superconducting quantum interference device 400 of the controllable impedance makes the reflection decline The resonant operational frequency of wave resonance chamber 200 is equal to frequency signal to be amplified, so that signal to be amplified and pump signal exists Nonlinear interaction is carried out in the reflection type microwave resonant cavity 200 and then amplifies signal to be amplified, signal to be amplified and pump After Pu signal carries out nonlinear interaction, includes not only signal to be amplified in output signal, further include various idler fi The frequency equal with one of idler frequency is set by the resonance frequency of the second microwave cavity 300, is made at this time Quantum parameters amplifier is in the pump signal frequency f of optimum working modepWithout being selected as f signal to be amplifiedsFrequency multiplication, from And when at a distance from the pump signal frequency of selection and frequency signal to be amplified have and can be split by filter, output each Idler fiAlso all with f signal to be amplifiedsWith the distance that can be split by filter, the present invention is micro- by being arranged described second Wave resonance chamber 300 is converted into the portion of energy of pump signal and the 300 resonance frequency phase of the second microwave cavity Deng a kind of idler, when the resonance frequency for selecting suitable second microwave cavity, then pass through second microwave resonance The resonance frequency of chamber 300 selects pump signal, can to generate and second microwave resonance in quantum parameters amplifier A kind of equal idler release of 300 resonance frequency of chamber, and in addition to other of the idler being released are all unrelated At a distance from signal can be split with the holding signal to be amplified on frequency spectrum by filter, and then these unrelated letters can be eliminated Number, improve the reading fidelity that quantum parameters amplifier reads signal to quantum bit.
It should be noted that in quantum calculation field, the operation result of quantum chip in order to obtain, it would be desirable to amount Signal, that is, quantum bit of sub- chip output reads signal and is acquired and analyzes, and it is extremely micro- that quantum bit reads detectable signal It is weak.By taking superconductive quantum bit system as an example, quantum bit reads detectable signal usually in 4-8GHz frequency range, power down to- 140dBm is hereinafter, even up to -150dBm or less.In view of quantum bit detectable signal and quantum bit read the coupling of detector Efficiency is closed, it is about 1-10 or so that the power of -150dBm to -140dBm, which corresponds to the photon numbers inside detector,.It is so micro- Weak detectable signal can also additionally incur loss after detector is spread out of again.Therefore, the application of quantum chip, needs The key problem of solution extracts effective quantum state information first is that how to read in signal from so faint quantum bit.
Assuming that the quantum bit that eventually off quantum bit reads detector, which reads signal, has 10 useful photons, they It will enter in subsequent route, mix with thermal noise, electrical noise etc..Wherein, the thermal noise of standard meets thermodynamics distribution, can To useIt is converted into number of photons n, k in above formulaBFor Boltzmann constant, T is that frequency is ambient noise at f Temperature, h are Planck's constant.Assuming that quantum chip is in 10mK temperature environment, then according to above formula, n can be ignored not less than 0.1 Meter.But the reception system that quantum bit reads signal is located at room temperature, n is about 1000, if quantum bit reading signal is straight It connects outflow to come, then can be submerged in noise.It therefore, the use of parameter amplifier is necessary.
Any amplifier all can extraly introduce noise while amplifying original signal.We usually with noise etc. Temperature, that is, noise are imitated to measure, the index is bigger, then noise is poorer.Amplifier is bound to deteriorate signal-to-noise ratio, therefore, puts The setting of big device should raise the gain of amplifier as much as possible, while controlling the noise temperature of amplifier.
Noise temperature equally meetsTherefore, it is making an uproar for f that we, which can convert noise temperature to frequency, Acousto-optic subnumber.And signal-to-noise ratio can be described as, the ratio of signal number of photons and noise light subnumber.
Commercial amplifier at present, the performance low-noise amplifier that most preferably Sweden LNF company produces, can amplify 4- The signal of 8GHz frequency range, noise temperature about 3K.It is measured with this, noise light subnumber is about 10, therefore most using commercial amplifiers The signal-to-noise ratio that can be obtained greatly is about 1, and best quantum parametric amplifier can achieve the noise level of standard quantum limit, Namely n=0.5.In general, n is fluctuated within 0.5-2.Therefore, usage amount subparameter amplifier can make the noise of system Than the promotion for having 5-20 times or so.
Although quantum parametric amplifier by way of greatly improving signal-to-noise ratio, is solved from so faint quantum bit The problem of extracting effective quantum state information in signal is read, but brings new problem.Existing quantum parameters amplification Device is worked based on non-linear frequency mixing principle, in order to effectively amplify quantum bit reading signal, so that quantum parameters are put The big device work pump signal close in the additional application frequency of optimal mode needs and frequency signal to be amplified or its frequency multiplication, example Such as corresponding pump signal applied close to it is signal to be amplified it is corresponding be four-wave mixing operating mode, the pump signal of application approaches Corresponding twice of frequency signal to be amplified is three wave mixing operating mode.
During quantum parameters amplifier operation, f signal to be amplified is inputtedsWith pump signal fp, f signal to be amplifieds? Pump signal fpUnder the action of amplify, export signal to be amplified, while being based on non-linear frequency mixing principle, further include in output signal The pump signal nf of frequency multiplicationp, half frequency pump signal 1/2fpAnd various idler fi, f signal to be amplifieds, pump signal fp And idler fiBetween will meet formula: mfs+nfi=lfp, in which: m, n and l are integer, and m, n and l take different numerical value When, obtain different idler fi.When quantum parameter amplifier is in four-wave mixing operating mode, pump signal fpFrequency It chooses close to f signal to be amplifiedsFrequency, in output signal, pump signal fpAnd the 2f in idlerp-fs、2fs-fpCause To approach f signal to be amplifiedsAnd influence acquisition signal to be amplified;When quantum parameter amplifier is in three wave mixing operating mode When, pump signal fpFrequency selection purposes are close to 2 times of f signal to be amplifiedsFrequency, in output signal, the pump signal 1/2f of half frequencyp And the f in idlerp-fsBecause close to f signal to be amplifiedsAnd influence acquisition signal to be amplified.
Specifically, referring to Fig. 1 and Fig. 2, the embodiment of the present invention one provides a kind of quantum parameters amplifier, the quantum ginseng Amount amplifier include it is sequentially connected for form the capacitance module 100 of oscillator-amplification circuit, reflection type microwave resonant cavity 200, The superconducting quantum interference device 400 of second microwave cavity 300 and controllable impedance, the superconductive quantum interference dress of the controllable impedance It sets 400 device one end and is connected to one end far from the capacitance module 100 of the reflection type microwave resonant cavity 200, another termination Ground;And the reflection type microwave resonance can be made by adjusting the inductance of the superconducting quantum interference device 400 of the controllable impedance The frequency of chamber 200 is equal to frequency signal to be amplified, in which: described signal to be amplified to be coupled into from the capacitance module 100 Enter the oscillator-amplification circuit, the oscillator-amplification circuit amplifies described signal to be amplified under the action of pump signal, and produces Raw several idler;
It should be noted that each described idler is all satisfied following formula:
mfs+nfi=lfp
Wherein: m, n, l are integer, fsFor frequency signal to be amplified, fpFor pump signal frequency, fiFor idler frequency, The resonance frequency of second microwave cavity 300 is equal with the frequency of one of idler, it should be noted that Above formula is based on non-linear frequency mixing principle, as f signal to be amplifiedsWith pump signal fpWhen determining, m, n and l take different numbers Value, will obtain various idler fi
Wherein, the capacitance module 100 is needed for being coupled into signal to be amplified in reflection type microwave resonant cavity 200 It is noted that usual microwave cavity must connect composition microwave system with external circuit to work, it is necessary to by external circuit Microwave signal motivate and establish oscillation in chamber, and the oscillation in chamber must can be just output on extraneous load by coupling, It generallys use capacitance module to couple with microwave cavity foundation, interdigital capacitor, distribution can be selected in capacitance module 100 in the present embodiment Formula capacitor or run-in index capacitor, the present invention for capacitance module 100 concrete form with no restrictions.
It should be noted that oscillator-amplification circuit is the common structure of signal amplification sector, it is the pass of many electronic equipments Key member, the usual form of expression of oscillator-amplification circuit are LC oscillating circuit, and capacitor and inductance including interconnection, it both can be used In the signal for generating specific frequency, it is also used for isolating the signal of specific frequency from more complicated signal.It is led in quantum calculation Domain, the in order to obtain operation result of quantum chip, it would be desirable to which signal is read to signal, that is, quantum bit of quantum chip output It is acquired and analyzes, usual quantum bit reading signal is very faint, needs to carry out signal amplification, since quantum bit is read Signal belongs to high-frequency signal, and wavelength is very short, and the capacitor and inductor device-structure dimensions used due to the LC oscillating circuit of lump Larger and LC oscillating circuit energy is Dispersed precipitate in surrounding space, and dissipative velocity is very fast, therefore we must make With the quantum parameters amplifier for being used in quantum regime.
In general, quantum parameters amplifier includes sequentially connected capacitor, microwave cavity, superconducting quantum interference device (SQUID) and use In the magnetic flux bias set circuti of modulation superconducting quantum interference device (SQUID), superconducting quantum interference device (SQUID) is grounded far from one end of resonant cavity, Basic principle is as follows: using the exchange electric forming inductance generated in superconducting quantum interference device (SQUID), LC oscillating circuit is constituted with capacitor, from And a single-mode field is constructed in microwave cavity, signal to be amplified and pump signal faint at this time enters device jointly In, it is signal to be amplified in microwave cavity to be amplified, while whole process is all in superconducting state, almost without dissipation.
Wherein: it should be noted that the superconducting quantum interference device (SQUID) is the closed loop being made of several Josephson junction parallel connections Device, in which: Josephson junction is generally made of two pieces of superconductor folders with certain very thin barrier layer, such as S (superconductor)- I (semiconductor or insulator)-S (superconductor) structure, abbreviation SIS, in SIS, superelectron can be from one of superconductor Side tunnels through semiconductor or insulator reaches the superconductor or Josephson effect of the other side, and the electric current of generation is known as Josephson current just constitutes Josephson's interferometer when multiple Josephson junctions are joined together to form closed-loop device, Or superconducting quantum interference device (SQUID).
It should be noted that workflow of the invention is as follows, by the superconductive quantum interference for adjusting the controllable impedance The inductance of instrument 400, so that the resonant frequency of operation of the reflection type microwave resonant cavity 200 is consistent with frequency signal to be amplified, So that signal to be amplified best in the 200 interior resonance amplification effect of reflection type microwave resonant cavity, by signal to be amplified and Pump signal is coupled into the reflection type microwave resonant cavity 200, signal to be amplified to put under the action of pump signal It greatly, further include pump signal, half frequency pump signal, frequency multiplication pump it should be noted that not only including amplified signal in output signal Pu signal and various idlers set the resonance frequency of the second microwave cavity 300 to and one of idler Frequency is equal, when selecting the resonance frequency of suitable second microwave cavity 300 to be f2, further according to relational expression mfs+nf2=lfp, Select suitable pump frequency fp, m=n=l=1 can be enabled to obtain a kind of pump frequency fp, generate in the oscillator-amplification circuit With the f2The equal idler of frequency will pass through second microwave cavity 300 and the superconducting quantum interference device (SQUID) device 400 ground connection outflows.
It should be noted that quantum parameters amplifier of the present invention is before operation, various parameters need to be designed, it is of the invention most The whole first purpose is so that will not interfere to signal to be amplified in the irrelevant signal of output, even if also they can be by Filter is split, and provides a kind of specific example here, when frequency signal to be amplified is 4GHz, can design one of which first Idler is 2GHz, and the resonance frequency f of second microwave cavity 300 is determined according to the idler2For 2GHz, pass through Relational expression mfs+nf2=lfp, m=n=l=1 is enabled to select suitable pump frequency fpFor 6Ghz, at this point, further according to formula mfs+ nfi=lfpWhen considering other possible idlers, it can be proved that work as m, when n and l take different numerical value, obtained idler fi It will not be to f signal to be amplifiedsIt interferes.Following table gives when frequency signal to be amplified is 4GHz, pump signal frequency is When 6GHz, generation with f signal to be amplifieds8 kinds of closest idler f of frequencyi
Table 1:8 kind idler 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
As seen from the above table, generation with f signal to be amplifieds8 kinds of closest idler f of frequencyiWith letter to be amplified Number fsCertain distance is kept, then other idlers f generatediIt will not be to f signal to be amplifiedsIt interferes.
Traditional quantum parameters amplifier there is a further problem, when practical quantum chip operation, it would be desirable to simultaneously A large amount of quantum bit signal is read, the quantum state information of each quantum bit carries outflow, frequency by an independent signal Rate and the frequency of the quantum state information carrying signal of other quantum bits are different.Simultaneously read multiple quantum bits it is meant that Simultaneously have it is multiple carry the signal to be amplified of information, need by quantum parametric amplifier.Wherein each signal exists for they While obtaining amplification effect, a large amount of irrelevant signal can be all generated, and wherein at least one irrelevant signal is waited for itself The signal of amplification is close.In addition to this, the irrelevant signal of some generation signal to be amplified, it is likely that extraly wait putting with another The frequency of big signal is close.
Specifically, for example: inputting the f signal to be amplified of traditional quantum parameters amplifiersFrequency be respectively 6.4GHz With 6.58GHz (at a distance of 0.18GHz, filter is detachable), traditional quantum parameters amplifier pumping signal fpFrequency can set It is calculated as 6.5GHz, corresponds to four-wave mixing operating mode, then according to formula mfs+nfi=lfp, the amplified signal f of 6.4GHzs One of idler fiFor 6.6GHz, it will influence 6.58GHz signal (at a distance of 0.02GHz, being difficult to split).
And when using quantum parameters amplifier of the invention, by designing an idler, such as 4GHz, according to the spare time Frequency signal determines the resonance frequency f of second microwave cavity 3002For 4GHz, according to the signal of 4GHz and 6.4GHz Amplified signal fsDesign pump signal fpFor 5.2GHz, it is known that according to the pump signal f of the 5.2GHzpRespectively with 6.4GHz With the amplified signal f of 6.58GHzsSignal mixer action, obtained all idler fiPut with 6.4GHz and 6.58Ghz Big signal fsKeep detachable distance.
Wherein, the superconducting quantum interference device 400 of the controllable impedance includes the superconductive quantum interference of Mutual Inductance Coupling connection Instrument 410 and Flux modulation circuit 420, specifically may refer to Fig. 2;The superconducting quantum interference device (SQUID) 410 is by several Josephsons The knot closed-loop device in parallel constituted;The Flux modulation circuit 420 is used for the magnetic flux by adjusting the closed-loop device Adjust the inductance of the superconducting quantum interference device (SQUID) 410.
The Flux modulation circuit 420 includes sequentially connected Flux modulation line and the electric current dress for generating bias current It sets;Wherein: the Flux modulation line is used for transmission the bias current, and makes the bias current and the superconductive quantum interference 410 Mutual Inductance Coupling of instrument.
It should be noted that the current device for generating bias current can be current source or be successively to connect What is connect can provide the voltage source and resistance of the bias current, and the present invention is without restriction for the concrete form of current source.
Further, it is the coplanar of wavelength a quarter signal to be amplified that the reflection type microwave resonant cavity 200, which is length, Waveguide microwave resonant cavity uses length for the co-planar waveguide microwave cavity of a quarter of wavelength signal to be amplified, due to four The electric field most strength of/mono- wavelength co-planar waveguide microwave cavity is located at close to one end of the capacitance module 100, and electric field is most Weak place is located at close to one end of the superconducting quantum interference device 300, and output signal will be leaned on from most strength is coupled close to signal One end output of the nearly capacitance module 100.
It should be noted that resonance frequency and the reflection type microwave resonant cavity when second microwave cavity 300 When 200 resonance frequency difference, in a kind of ideler frequency identical with its resonance frequency of the resonance of second microwave cavity 300 Signal will be unable to enter in the reflection type microwave resonant cavity 200.
It should be noted that co-planar waveguide is prepared on three parallel metal foils of dielectric layer surface in microwave regime Film conduction band layer, wherein centrally located conduction band layer is used for transmission microwave signal, the conduction band layer of two sides is all connected to ground level, with one As the maximum difference of circuit be that co-planar waveguide is a kind of distributed circuit elements, capacitive/inductive/impedance/impedance equably edge Co-planar waveguide signal propagation direction distribution, co-planar waveguide propagate be TEM wave, along signal propagation direction, the impedance of waveguide Equal everywhere, because signal reflex may be not present, signal almost can nondestructively pass through;In addition, the not cut-off frequency of co-planar waveguide, And there is cutoff frequency in common lumped circuitry.For co-planar waveguide uniform for one section, most frequency ranges it is micro- Wave signal can transmit unblockedly, thus be called transmission line, i.e. coplanar waveguide transmission line.When the coplanar wave guide transmission of design Line has certain length, and constructs a capacitive node respectively at the both ends of coplanar waveguide transmission line, and microwave signal encounters node Back reflection forms resonance in this section of transmission line, constitutes resonant cavity.
Preferably, coplanar waveguide transmission line can also be used in the Flux modulation line for being used for transmission the bias current.
Preferably, second microwave cavity 300 is grounded far from one end of the reflection type microwave resonant cavity 200, such as This setting can make the idler of the generation of the second microwave cavity 300 or be flowed out by the ground connection.
Further, referring to Fig. 3, due to it is amplified it is signal to be amplified will be from the close of reflection type microwave resonant cavity 200 The side of the capacitance module 100 is exported via the capacitance module 100, for the signal to be amplified and output signal that will be inputted It is isolated, the quantum parameters amplifier further includes circulator 500, and the circulator 500 is arranged in the capacitance module 100 One end far from the reflection type microwave resonant cavity 200.
Further, referring to Fig. 3, in order to filter out the irrelevant signal in output signal other than amplified signal, in institute The signal output end for stating circulator 500 is additionally provided with filter 600, wherein irrelevant signal generally refers to pump signal, half frequency Pump signal, frequency multiplication pump signal and various idlers.
Further, the quantum parameters amplifier further includes voltage modulation circuit 700;The voltage modulation circuit 700 are arranged in the superconducting quantum interference device 400 of the controllable impedance close to described 200 one end of reflection type microwave resonant cavity;Institute The superconducting quantum interference device (SQUID) device 300 for stating controllable impedance can be in the effect of the bias voltage of the voltage modulation circuit 700 offer It is lower to discharge one of idler generated in the oscillator-amplification circuit.
It should be noted that passing through the electricity of Josephson junction when applying voltage bias at superconducting quantum interference device (SQUID) both ends Stream is the oscillation supercurrent an of alternation, and frequency of oscillation (or Josephson's frequency) will be directly proportional to the bias voltage, this So that Josephson junction has the ability of radiation or electromagnetic wave absorption, meet following relational expression:
2eV=hf
Wherein: h is Planck's constant.
Since the superconducting quantum interference device (SQUID) device being made of several Josephson junction parallel connections has the ability of electromagnetic wave absorption, When applying voltage bias on the superconducting quantum interference device (SQUID) device 400 in the controllable impedance, electric current library that Josephson ties Uncle is grounded outflow to the energy tunnelling Josephson junction that will absorb microwave signal, when selecting suitable voltage bias, so that closing It is the frequency that f is equal to one of idler that oscillator-amplification circuit generates in formula 2eV=hf, is generated in oscillator-amplification circuit The idler will be completely absorbed, show as the idler and be released.
It should be noted that when the bias voltage applied makes the superconducting quantum interference device (SQUID) device 400 of the controllable impedance When the frequency of the idler of release is equal to the resonance frequency of second microwave cavity 300, active is reinforced believing pumping Number portion of energy be converted into the ability of the idler equal with the resonance frequency of second microwave cavity, also, by It is connected to electric field the weakest point of the reflection type microwave resonant cavity 200 in the voltage modulation circuit 700, passes through voltage modulated electricity The DC voltage bias that road 700 exports is nearly free from influence to the microwave signal in the reflection type microwave resonant cavity 200.
It should be noted that existing quantum parameter amplifier, only when pump signal frequency is equal to frequency signal to be amplified Integral multiple when, be just able to achieve maximum amplification effect.Under corresponding three wave mixing operating mode, pump signal frequency is equal to wait put Big signal frequency.Under four-wave mixing operating mode, pump signal frequency is equal to twice of frequency signal to be amplified.Three wave mixing work Pump signal and the bad differentiation of amplified signal under operation mode, in output signal.And under four-wave mixing operating mode, output signal In half frequency pump signal and the bad differentiation of amplified signal.Using a kind of quantum parameters amplifier of the present invention, make quantum at this time Parameter amplifier is in the pump signal frequency of optimum working mode without being selected as frequency multiplication signal to be amplified, when selection is suitable The second microwave cavity resonance frequency and pump signal when, each nothing generated in quantum parameters amplifier can be made At a distance from OFF signal can be split with the holding signal to be amplified on frequency spectrum by filter, and then rear class filtering can be used Device easily eliminates these irrelevant signals, improves the reading fidelity that quantum parameters amplifier reads signal to quantum bit.
Structure, feature and effect of the invention, the above institute are described in detail based on the embodiments shown in the drawings Only presently preferred embodiments of the present invention is stated, but the present invention does not limit the scope of implementation as shown in the drawings, it is all according to structure of the invention Think made change or equivalent example modified to equivalent change, when not going beyond the spirit of the description and the drawings, It should all be within the scope of the present invention.

Claims (13)

1. a kind of quantum parameters amplifier, it is characterised in that: quantum parameters amplifier includes:
The superconduction of the sequentially connected capacitance module, reflection type microwave resonant cavity and controllable impedance for being used to form oscillator-amplification circuit Quantum interference device;A termination of the superconducting quantum interference device of the controllable impedance far from the reflection type microwave resonant cavity Ground;
It can make the humorous of the reflection type microwave resonant cavity by adjusting the inductance of the superconducting quantum interference device of the controllable impedance Vibration frequency is equal to frequency signal to be amplified, in which: described signal to be amplified the vibration to be coupled into from the capacitance module Swing amplifying circuit, the oscillator-amplification circuit amplifies described signal to be amplified under the action of pump signal, and generates several Idler, the quantum parameters amplifier further include the second microwave cavity, and second microwave cavity is connected to described The one end of reflection type microwave resonant cavity far from the capacitance module, in which: the resonance frequency of second microwave cavity and its A kind of frequency of middle idler is equal.
2. quantum parameters amplifier according to claim 1, which is characterized in that the superconductive quantum interference of the controllable impedance Device includes the superconducting quantum interference device (SQUID) and Flux modulation circuit of Mutual Inductance Coupling connection;
The superconducting quantum interference device (SQUID) is the closed-loop device being made of several Josephson junction parallel connections;
The Flux modulation circuit is used to adjust the superconductive quantum interference by the magnetic flux for adjusting the closed-loop device The inductance of instrument.
3. quantum parameters amplifier according to claim 2, which is characterized in that the superconducting quantum interference device (SQUID) is by two The closed-loop device that Josephson junction parallel connection is constituted.
4. quantum parameters amplifier according to claim 2, which is characterized in that the Flux modulation circuit includes successively connecting The Flux modulation line connect and the current device for generating bias current;
Wherein: the Flux modulation line is used for transmission the bias current, and keeps the bias current and the Superconducting Quantum dry Interferometer Mutual Inductance Coupling.
5. quantum parameters amplifier according to claim 4, which is characterized in that the Flux modulation line is that co-planar waveguide is micro- Band transmission line.
6. quantum parameters amplifier according to claim 4, which is characterized in that the current device be current source or according to Secondary connection can provide the voltage source and resistance of the bias current.
7. quantum parameters amplifier according to claim 2, which is characterized in that for amplifying the pump signal to be amplified Pu signal is coupled into the oscillator-amplification circuit from the capacitance module or the Flux modulation circuit.
8. quantum parameters amplifier according to claim 1, which is characterized in that the capacitance module is interdigital capacitor, divides Cloth capacitor and run-in index capacitor are one of.
9. quantum parameters amplifier according to claim 1, which is characterized in that the reflection type microwave resonant cavity is length For the co-planar waveguide microwave cavity of the wavelength a quarter signal to be amplified.
10. quantum parameters amplifier according to claim 1, which is characterized in that the quantum parameters amplifier further includes Voltage modulation circuit;
The superconducting quantum interference device that the controllable impedance is arranged in the voltage modulation circuit is humorous close to the reflection type microwave Shake chamber one end;
The effect for the bias voltage that the superconducting quantum interference device (SQUID) device of the controllable impedance can be provided in the voltage modulation circuit The lower idler equal with the resonance frequency of second microwave cavity that will be generated in the oscillator-amplification circuit discharges.
11. quantum parameters amplifier according to claim 1, which is characterized in that second microwave cavity is far from institute State one end ground connection of reflection type microwave resonant cavity.
12. -11 described in any item quantum parameters amplifiers according to claim 1, which is characterized in that the quantum parameters amplification Device further includes circulator;
The one end of the capacitance module far from the reflection type microwave resonant cavity is arranged in the circulator, for by described wait put Big signal inputs the oscillator-amplification circuit, and the output signal that the oscillator-amplification circuit is generated exports.
13. quantum parameters amplifier according to claim 12, which is characterized in that the quantum parameters amplifier further includes Filter;
The one end of the circulator far from the capacitance module is arranged in the filter.
CN201910522955.6A 2019-06-17 2019-06-17 A kind of quantum parameters amplifier Pending CN110120792A (en)

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