WO2021253404A1 - 量子态编码装置、方法及量子处理器 - Google Patents

量子态编码装置、方法及量子处理器 Download PDF

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WO2021253404A1
WO2021253404A1 PCT/CN2020/097106 CN2020097106W WO2021253404A1 WO 2021253404 A1 WO2021253404 A1 WO 2021253404A1 CN 2020097106 W CN2020097106 W CN 2020097106W WO 2021253404 A1 WO2021253404 A1 WO 2021253404A1
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quantum state
quantum
encoding
qubit
state
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PCT/CN2020/097106
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French (fr)
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刘丰铭
陈明城
王粲
应翀
王建文
张宇宸
尚仲夏
陆朝阳
潘建伟
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中国科学技术大学
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    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06N—COMPUTING ARRANGEMENTS BASED ON SPECIFIC COMPUTATIONAL MODELS
    • G06N10/00—Quantum computing, i.e. information processing based on quantum-mechanical phenomena

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  • the present disclosure relates to the technical field of quantum computers, and in particular to a quantum state encoding device, method, and quantum processor.
  • Quantum computers are devices that use quantum states to encode and calculate information. Compared with traditional computers, the computational efficiency of quantum computers has been improved exponentially, and it has great potential in solving complex problems. Thanks to the support of modern micro-nano processing technology, superconducting quantum computing is easy to achieve large-scale integration, and it has become the most rapidly developing method currently.
  • Superconducting qubits are actually encoded using the quantum states of superconducting circuits.
  • the most widely used is the Transmon qubit.
  • the Fluxonium bit which is a qubit structure formed by an inductance composed of approximately a Josephson junction array and a small Josephson junction in parallel, and uses the ground state quantum states in different potential wells in the phase space for encoding. It is not affected by charge noise, but it is more sensitive to magnetic flux noise, the phase decoherence time is short, and it is not easy to manipulate, so it has not yet been substantively applied.
  • the present disclosure provides a quantum state encoding device, method, and quantum processor.
  • the two quantum states with the lowest energy in a potential well with the lowest energy are used for encoding, which has a faster control speed and is less susceptible to magnetic flux. Noise influence, longer phase decoherence time, easy to control, and easy to realize multi-bit coupling.
  • the device includes: a qubit structure 1 having N potential wells in a phase space, and the first potential well is the potential well with the lowest energy among the N potential wells , There are M quantum states in the first potential well, N is an integer greater than 0, and M is an integer greater than 1.
  • the encoding module 2 uses the first quantum state and the second quantum state as logical bits for encoding, the The first quantum state and the second quantum state are the two quantum states with the lowest energy among the M quantum states.
  • the distribution ratio of the first quantum state in the first potential well in the phase space and the distribution ratio of the second quantum state in the first potential well in the phase space are not less than a preset threshold.
  • the device further includes: a magnetic flux control module 3 for controlling the magnetic flux input into the qubit structure 1 to control the energy level difference between the first quantum state and the second quantum state.
  • a magnetic flux control module 3 for controlling the magnetic flux input into the qubit structure 1 to control the energy level difference between the first quantum state and the second quantum state.
  • the device further includes: a transition control module 4, configured to control the microwave pulse input into the qubit structure 1 to control the qubit structure 1 in the first quantum state and the second quantum state. Transition between states.
  • a transition control module 4 configured to control the microwave pulse input into the qubit structure 1 to control the qubit structure 1 in the first quantum state and the second quantum state. Transition between states.
  • the qubit structure 1 is composed of a capacitor structure 11, a Josephson junction structure 12, and an inductance structure 13 in parallel.
  • the inductance structure 13 is composed of multiple Josephson junctions in series or multiple inductors in parallel
  • the capacitor structure 11 is composed of multiple capacitors in parallel
  • the Josephson junction structure 12 is composed of multiple Josephson junctions. Composed in parallel.
  • the device further includes: a reading module 5 for reading the quantum state of the qubit structure 1 and transmitting the read quantum state to the encoding module 2.
  • Another aspect of the present disclosure provides a method for encoding by the quantum state encoding device as described above.
  • the method includes: selecting the first quantum state and the second quantum state in the qubit structure 1 as calculation basis vectors for encoding.
  • the selecting the first quantum state and the second quantum state in the qubit structure 1 as calculation basis vectors for encoding includes: using the magnetic flux control module 3 to control one of the first quantum state and the second quantum state Use the transition control module 4 to control the quantum state in the qubit structure 1 to transition between the first quantum state and the second quantum state; use the encoding module 2 to obtain the quantum state in the qubit structure 1, and according to the quantum The first quantum state and the second quantum state in the bit structure 1 are encoded.
  • Another aspect of the present disclosure provides a quantum processor, which includes the quantum state encoding device as described above.
  • the quantum state encoding device, method, and quantum processor provided by the embodiments of the present disclosure have the following beneficial effects:
  • transition frequency is less sensitive to external magnetic flux, is not easily affected by magnetic flux noise, and has a longer phase decoherence time
  • Fig. 1 schematically shows a structural diagram of a quantum state encoding device provided by an embodiment of the present disclosure
  • Figure 2 schematically shows a structural diagram of a qubit structure in a quantum state encoding device provided by an embodiment of the present disclosure
  • 3A schematically shows a potential well and a wave function diagram of a quantum state in the potential well in the quantum state encoding device provided by an embodiment of the present disclosure
  • FIG. 3B schematically shows another potential well in the quantum state encoding device provided by an embodiment of the present disclosure and a wave function diagram of a quantum state in the potential well;
  • 4A schematically shows the relationship between the transition frequency and the applied magnetic flux in the quantum state encoding device provided by an embodiment of the present disclosure
  • Fig. 4B schematically shows the relationship between the sensitivity of the transition frequency to the applied magnetic flux and the adjustment size of the transition frequency in the quantum state encoding device provided by an embodiment of the present disclosure
  • FIG. 5 schematically shows a flowchart of a method for encoding by a quantum state encoding device provided by an embodiment of the present disclosure
  • Fig. 6 schematically shows a schematic structural diagram of a quantum processor provided by an embodiment of the present disclosure.
  • Fig. 1 schematically shows a schematic structural diagram of a quantum state encoding device provided by an embodiment of the present disclosure. Referring to FIG. 1, and in conjunction with FIG. 2 to FIG. 4B, the quantum state encoding device in this embodiment will be described in detail.
  • the quantum state encoding device includes a qubit structure 1, an encoding module 2, a magnetic flux control module 3, a transition control module 4 and a reading module 5.
  • the qubit structure 1 has N potential wells in the phase space.
  • the first potential well is the potential well with the lowest energy among the N potential wells.
  • M quantum states in the first potential well and N is an integer greater than 0, M Is an integer greater than 1.
  • the qubit structure 1 is composed of a capacitor structure 11, a Josephson junction structure 12 and an inductance structure 13 in parallel.
  • the capacitor structure 11 may be composed of one capacitor, or may be composed of multiple capacitors in parallel.
  • the Josephson junction structure 12 can be composed of one Josephson junction, or can be composed of multiple Josephson junctions in parallel.
  • the inductance structure 13 can be composed of a plurality of approximately Sirfson junctions in series, or can be composed of multiple inductors in parallel, and can also be composed of a approximately Sirfson junction or inductance.
  • the Josephson junction has a larger capacitance value and also a larger size.
  • a loop is formed between the Josephson junction structure 12 and the inductance structure 13, and an adjustable magnetic flux ⁇ ext passes through the loop.
  • Hamiltonian of qubit structure 1 for:
  • E C is the charge energy in the capacitor structure 11
  • e is the elementary charge
  • C is the capacitance value of the capacitor structure 11
  • E J is the Josephson energy of Josephson junction structure 12
  • E J is determined by the structure of Josephson junction structure 12.
  • ⁇ ext is the magnetic flux passing through the Josephson junction structure 12 and the inductance structure
  • ⁇ 0 is the magnetic flux quantum
  • ⁇ 0 h/2e
  • h is the Planck constant
  • EL is the inductance
  • L is the inductance value of the inductance structure 13.
  • Hamiltonian of qubit structure 1 middle Is the potential energy term, denoted as The potential energy term
  • the potential energy term Related to the external magnetic flux ⁇ ext , changing the size of ⁇ ext can change the shape of the potential well of the qubit structure 1, thereby adjusting the transition frequency of the qubit structure 1.
  • E L can inductance, the greater the adjustment range of the transition frequency, the coding apparatus quantum state transition frequency may be adjusted while ensuring sensitivity with a smaller bit frequency magnetic flux noise.
  • the parameter settings of the capacitance structure 11, the Josephson junction structure 12 and the inductance structure 13 in the qubit structure 1 need to meet the following conditions: the qubit structure 1 has N potential wells in the phase space, and N is greater than 0 An integer of, N ⁇ 1; M quantum states exist in the first potential well with the lowest energy among the N potential wells, and M is an integer greater than 1, M ⁇ 2; the two quantum states with the lowest energy among the M quantum states ( That is, the distribution ratio of the first quantum state and the second quantum state) in the phase space in the first potential well is not less than the preset threshold.
  • the distribution ratio of the first quantum state in the first potential well in the phase space and the distribution ratio of the second quantum state in the first potential well in the phase space are not less than a preset threshold.
  • a preset threshold can be set according to actual application requirements.
  • the magnetic flux control module 3 is used to control the magnetic flux input into the qubit structure 1 to control the energy level difference between the first quantum state and the second quantum state, that is, to control the transition between the first quantum state and the second quantum state frequency.
  • the transition control module 4 is used to control the microwave pulse input into the qubit structure 1, and the frequency of the microwave pulse is equal to the transition frequency between the first quantum state and the second quantum state, thereby controlling the qubit structure 1 from the first quantum state Transition to the second quantum state, or control the quantum bit structure 1 to transition from the second quantum state to the first quantum state.
  • the quantum state in the qubit structure 1 transitions between the first quantum state and the second quantum state, and the quantum state read by the reading module 5 from the qubit structure 1 is between the first quantum state and the second quantum state , And send the read quantum state to the encoding module 2.
  • the encoding module 2 uses the first quantum state and the second quantum state in the qubit structure 1 as logical bits for encoding. Specifically, the reading module 5 reads the quantum state of the qubit structure 1, and transmits the energy value of the read quantum state to the encoding module 2. When the quantum state read by the reading module 5 is the first quantum state Or in the second quantum state, the encoding module 2 generates a corresponding encoding according to the energy value of the quantum state read by the reading module 5. Taking the energy of the first quantum state lower than the energy of the second quantum state as an example, the first quantum state corresponds to the logical bit "0", and the second quantum state corresponds to the logical bit "1".
  • the encoding module 2 When the qubit structure 1 is in the first quantum When the state, the encoding module 2 generates a code “0”, and when the transition control module 4 controls the quantum bit structure 1 to transition from the first quantum state to the second quantum state, the encoding module 2 generates a code “1”.
  • the qubit in this embodiment transitions between the first quantum state and the second quantum state. During the transition, the phase center changes little, which is a plasma oscillation transition (Plasmon transition). Therefore, the quantum in this embodiment
  • the bit can be named Plasonium qubit. Taking the qubit structure 1 corresponding to FIG. 3B as an example, the control performance, noise sensitivity, etc. of the quantum state encoding device in this embodiment are analyzed.
  • the anharmonicity of the qubit structure 1 is related to the applied magnetic flux ⁇ ext .
  • the anharmonicity where the external magnetic flux is 0 is the smallest, about 650MHz, and the maximum can reach 1.5GHz.
  • the anharmonicity of Transmon qubits widely used in the prior art is about 200MHz-250MHz. Based on this, it can be seen that the anharmonicity of the qubit in this embodiment is more than 3 times that of the Transmon qubit. Therefore, the control speed of the qubit in this embodiment is at least 3 times that of the Transmon qubit, which has faster control. speed.
  • the charge transition matrix element of the qubit It is 0.6-0.7, thus, single-bit manipulation and multi-bit coupling can be realized through capacitive coupling.
  • FIG. 4A the relationship between the qubit transition frequency and the applied magnetic flux is shown in FIG. 4A.
  • the transition frequency in this embodiment can be adjusted at least 700 MHz.
  • Figure 4B shows the relationship between the magnetic flux noise sensitivity of three different qubits and the adjustment of the transition frequency. It can be seen that when the transition frequency changes the same, the quantum in this embodiment The frequency of the bit has the least sensitivity to the external magnetic flux. Therefore, the quantum state encoding device can adjust the transition frequency while maintaining a low sensitivity to magnetic flux noise.
  • Another embodiment of the present disclosure provides a method for encoding using the quantum state encoding device in the embodiment shown in FIG. 1 to FIG. 4B.
  • the method includes: selecting the first quantum state and the second quantum in the qubit structure 1
  • the state is coded as a calculation basis vector.
  • FIG. 5 schematically shows a flowchart of a method for encoding by a quantum state encoding device provided by an embodiment of the present disclosure.
  • the operation of selecting the first quantum state and the second quantum state in the qubit structure 1 as calculation basis vectors for encoding includes operations S510-S530.
  • the magnetic flux control module 3 is used to control the energy level difference between the first quantum state and the second quantum state. Specifically, the magnetic flux control module 3 is used to control the magnetic flux input into the qubit structure 1 so as to control the energy level difference between the first quantum state and the second quantum state.
  • the transition control module 4 is used to control the quantum state in the qubit structure 1 to transition between the first quantum state and the second quantum state. Specifically, the transition control module 4 is used to control the microwave pulse input into the qubit structure 1, thereby controlling the qubit structure 1 to transition from the first quantum state to the second quantum state, or control the qubit structure 1 to transition from the second quantum state To the first quantum state.
  • the encoding module 2 obtains the quantum state in the qubit structure 1, and performs encoding according to the first quantum state and the second quantum state in the qubit structure 1. Specifically, the encoding module 2 reads the quantum state in the qubit structure 1 through the reading module 5, and generates a corresponding encoding "0" or "1" according to the read quantum state.
  • Fig. 6 schematically shows a schematic structural diagram of a quantum processor provided by an embodiment of the present disclosure.
  • the quantum processor includes the quantum state encoding device in the embodiment shown in FIG. 1 to FIG. 4B.
  • the quantum processor is composed of K quantum state encoding devices, K>1.
  • the shaded part in the figure is the superconductor on a two-dimensional plane, and the unshaded part is the dielectric layer without the superconductor attached.
  • the quantum processor includes K qubit structures 1, K magnetic flux control modules 3, K transition control modules 4, and K reading modules 5, qubit structure 1, magnetic flux control module 3, and transition control module There is a one-to-one correspondence between 4 and the reading module 5, and the K qubit structures 1 are coupled together through a capacitor structure 11.
  • the magnetic flux control module 3 is, for example, a low-frequency microwave transmission line, which is used as a magnetic flux control line to adjust the transition frequency of the qubit structure 1 and implement operations such as phase gates.
  • the transition control module 4 is, for example, a high-frequency microwave transmission line as a transition control line to control the quantum state of the qubit structure 1 to transition between the first quantum state and the second quantum state.
  • the reading module 5 is, for example, a linear resonant cavity, and the linear resonant cavity is coupled with the qubit structure 1 and reads the quantum state of the qubit structure 1 by means of dispersion measurement.
  • the quantum processor has strong compatibility with existing supporting equipment and systems, and is convenient for large-scale applications in the future.

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Abstract

本公开提供了一种量子态编码装置、方法及量子处理器。所述装置包括：量子比特结构(1)，在相位空间中具有N个势阱，第一势阱为N个势阱中能量最低的势阱，第一势阱中存在M个量子态，N为大于0的整数，M为大于1的整数；编码模块(2)，利用第一量子态和第二量子态作为逻辑比特进行编码，第一量子态和第二量子态为M个量子态中能量最低的两个量子态。利用一能量最低的势阱中能量最低的两个量子态进行编码，具有更快的操控速度，不易受磁通噪声影响，具有更长的相位退相干时间，易于操控，便于实现多比特耦合。。

Description

量子态编码装置、方法及量子处理器 技术领域
本公开涉及量子计算机技术领域，具体地，涉及一种量子态编码装置、方法及量子处理器。
背景技术
量子计算机是利用量子态对信息进行编码和计算的设备。相对于传统计算机，量子计算机的运算效率具有指数级的提高，在解决复杂问题方面具有巨大潜力。由于现代微纳加工技术的支持，超导量子计算易于实现大规模集成，成为当前发展最为迅速的方式。
超导量子比特实际上是利用超导电路的量子态来进行编码的。相关技术中，应用最广泛的是Transmon量子比特。但是其为了降低电荷噪声的影响减少了比特的非简谐性，导致比特的操控速度受到限制。另一种量子比特为Fluxonium比特，它是以大约瑟夫森结阵列组成的电感与小约瑟夫森结并联所形成的量子比特结构，并且采用相位空间中不同势阱中的基态量子态进行编码，其不受电荷噪声的影响，但是其对磁通噪声较为敏感，相位退相干时间较短，并且不易操控，从而尚未得到实质性的应用。
发明内容
(一)要解决的技术问题
本公开鉴于上述问题，提供了一种量子态编码装置、方法及量子处理器，利用一能量最低的势阱中能量最低的两个量子态进行编码，具有更快的操控速度，不易受磁通噪声影响，具有更长的相位退相干时间，易于操控，便于实现多比特耦合。
(二)技术方案
本公开一方面提供了一种量子态编码装置，所述装置包括：量子比特结构1，在相位空间中具有N个势阱，第一势阱为所述N个势阱中能量最低的势阱，所述第一势阱中存在M个量子态，N为大于0的整数，M为大于1的整数；编码模块2，利用第一量子态和第二量子态作为逻辑比特进行编码，所述第一量子态和第二量子态为所述M个量子态中能量最低的两个量子态。
可选地，所述第一量子态在相位空间中在第一势阱中的分布比例、所述第二量子态在相位空间中在第一势阱中的分布比例不小于预设阈值。
可选地，所述装置还包括：磁通控制模块3，用于控制输入至所述量子比特结构1中的磁通量，以控制所述第一量子态和第二量子态之间的能级差。
可选地，所述装置还包括：跃迁控制模块4，用于控制输入至所述量子比特结构1中的微波脉冲，以控制所述量子比特结构1在所述第一量子态与第二量子态之间跃迁。
可选地，所述量子比特结构1由电容结构11、约瑟夫森结结构12和电感结构13并联组成。
可选地，所述电感结构13由多个大约瑟夫森结串联或者由多个电感并联组成，所述电容结构11由多个电容并联组成，所述约瑟夫森结结构12由多个约瑟夫森结并联组成。
可选地，所述装置还包括：读取模块5，用于读取所述量子比特结构1的量子态，并将读取到的量子态传输至所述编码模块2。
本公开另一方面提供了一种如上所述的量子态编码装置进行编码的方法，所述方法包括：选取量子比特结构1中的第一量子态和第二量子态作为计算基矢进行编码。
可选地，所述选取量子比特结构1中的第一量子态和第二量子态作为计算基矢进行编码，包括：利用磁通控制模块3控制所述第一量子态和第二量子态之间的能级差；利用跃迁控制模块4控制量子比特结构1中的量子态在第一量子态和第二量子态之间跃迁；利用编码模块2获取 量子比特结构1中的量子态，并根据量子比特结构1中的第一量子态和第二量子态进行编码。
本公开另一方面提供了一种量子处理器，所述量子处理器包括如上所述的量子态编码装置。
(三)有益效果
本公开实施例提供的量子态编码装置、方法及量子处理器，具有以下有益效果：
(1)用于编码的第一量子态和第二量子态之间波函数重叠较大，使得电荷跃迁矩阵元较大，可以通过电容耦合的方式进行单比特操控与多比特耦合，简单快速，易于操控；
(2)跃迁频率对外加磁通敏感程度比较小，不易受到磁通噪声的影响，具有更长的相位退相干时间；
(3)具有较大的非简谐性，从而具有更快的操控速度，并且能够避免量子比特激发到计算空间之外；
(4)具有更长的比特寿命，从而实现更高的操控精度。
附图说明
图1示意性示出了本公开实施例提供的量子态编码装置的结构示意图；
图2示意性示出了本公开实施例提供的量子态编码装置中量子比特结构的结构图；
图3A示意性示出了本公开实施例提供的量子态编码装置中一势阱及势阱中量子态的波函数图；
图3B示意性示出了本公开实施例提供的量子态编码装置中另一势阱及势阱中量子态的波函数图；
图4A示意性示出了本公开实施例提供的量子态编码装置中跃迁频率与外加磁通的关系图；
图4B示意性示出了本公开实施例提供的量子态编码装置中跃迁频 率对外加磁通敏感度与跃迁频率调整大小的关系图；
图5示意性示出了本公开实施例提供的量子态编码装置进行编码的方法的流程图；
图6示意性示出了本公开实施例提供的量子处理器的结构示意图。
附图标记说明：
1-量子比特结构；
11-电容结构；
12-约瑟夫森结结构；
13-电感结构；
2-编码模块；
3-磁通控制模块；
4-跃迁控制模块；
5-读取模块。
具体实施方式
为使本发明的目的、技术方案和优点更加清楚明白，以下结合具体实施例，并参照附图，对本发明作进一步的详细说明。
图1示意性示出了本公开实施例提供的量子态编码装置的结构示意图。参阅图1，同时结合图2-图4B，对本实施例中的量子态编码装置进行详细说明。
参阅图1，该量子态编码装置包括量子比特结构1、编码模块2、磁通控制模块3、跃迁控制模块4和读取模块5。
量子比特结构1在相位空间中具有N个势阱，第一势阱为这N个势阱中能量最低的势阱，第一势阱中存在M个量子态，N为大于0的整数，M为大于1的整数。
具体地，参阅图2，量子比特结构1由电容结构11、约瑟夫森结结构12和电感结构13并联组成。电容结构11可以由一个电容组成，也可以由多个的电容并联后组成。约瑟夫森结结构12可以由一个约瑟夫森结组成，也可以由多个约瑟夫森结并联后组成。电感结构13可以由 多个大约瑟夫森结串联组成，也可以由多个电感并联组成，还可以由一个大约瑟夫森结或电感组成。与常规约瑟夫森结不同的是，大约瑟夫森结具有更大电容值，同时也具有更大的尺寸。
约瑟夫森结结构12和电感结构13之间形成回路，该回路中穿过有大小可调的磁通Φ ext。量子比特结构1的哈密顿量
Figure PCTCN2020097106-appb-000001
为：
Figure PCTCN2020097106-appb-000002
E C＝e 2/2C     (2)
E L＝(Φ 0/2π) 2/L    (3)
其中，E C为电容结构11中的电荷能，e为元电荷，C为电容结构11的电容值，
Figure PCTCN2020097106-appb-000003
为量子比特结构1中一结点上的库珀对数目，E J为约瑟夫森结结构12的约瑟夫森能，E J由约瑟夫森结结构12的结构确定，
Figure PCTCN2020097106-appb-000004
为电感结构13两端的相位差，Φ ext为穿过约瑟夫森结结构12和电感结构13的磁通量，Φ 0为磁通量子，Φ 0＝h/2e，h为普朗克常数，E L为电感结构13中的电感能，L为电感结构13的电感值。
量子比特结构1的哈密顿量
Figure PCTCN2020097106-appb-000005
中，
Figure PCTCN2020097106-appb-000006
为势能项，记为
Figure PCTCN2020097106-appb-000007
该势能项
Figure PCTCN2020097106-appb-000008
与外加磁通Φ ext相关，改变Φ ext的大小可以改变量子比特结构1的势阱形状，从而调整量子比特结构1的跃迁频率。电感能E L越大，跃迁频率的调整范围越大，该量子态编码装置可以在调节跃迁频率的同时，保证比特频率对磁通噪声具有较小的敏感度。
量子比特结构1中电容结构11、约瑟夫森结结构12和电感结构13的参数不同时，相位空间中出现的势阱也不相同。本实施例中，量子比特结构1中电容结构11、约瑟夫森结结构12和电感结构13的参数设置需满足以下条件：使得量子比特结构1在相位空间中具有N个势阱，N为大于0的整数，N≥1；N个势阱中能量最低的第一势阱中存在M个量子态，M为大于1的整数，M≥2；M个量子态中能量最低的两个量子态(即第一量子态和第二量子态)在相位空间中在第一势阱中的分布比例不小于预设阈值。
本实施例中，第一量子态在相位空间中在第一势阱中的分布比例、第二量子态在相位空间中在第一势阱中的分布比例不小于预设阈值。由 此，避免第一量子态和第二量子态在别的势阱中分布较多而导致量子比特结构1的跃迁频率对磁通噪声较为敏感，降低了量子比特结构1的跃迁频率对磁通噪声的敏感度。但是第一量子态与第二量子态在相位空间中的分布还对比特跃迁频率的调节范围等方面存在影响。实际应用中，可以根据实际应用要求来设置上述预设阈值。
量子比特结构1中电容结构11的电容值C、约瑟夫森结结构12的结构参数、电感结构13的电感值L选取的参数使得E C＝0.8GHz、E J＝5GHz、E L＝0.4GHz，外加磁通Φ ext为0时，量子比特结构1的势能如图3A所示。参阅图3A，可知相位空间中，在
Figure PCTCN2020097106-appb-000009
为-2π、0、2π附近均存在一个势阱，并且
Figure PCTCN2020097106-appb-000010
处的势阱最低，在
Figure PCTCN2020097106-appb-000011
处的势阱中存在两个量子态，这两个量子态的相位分布大部分限制在
Figure PCTCN2020097106-appb-000012
处的势阱范围内，即该两个量子态在
Figure PCTCN2020097106-appb-000013
处的势阱中的部分在该两个量子态中的占比均大于预设阈值，因此，可以选用这两个量子态作为逻辑比特进行编码。具体地，选用能量最小的量子态(图3A中虚线)表示逻辑“0”，选用能量次小的量子态(图3A中实线)表示逻辑“1”。
量子比特结构1中电容结构11的电容值C、约瑟夫森结结构12的结构参数、电感结构13的电感值L选取的参数使得E C＝0.8GHz、E J＝5GHz、E L＝2GHz，外加磁通Φ ext为0时，量子比特结构1的势能如图3B所示。参阅图3B，可知相位空间中，仅在
Figure PCTCN2020097106-appb-000014
为0附近均存在一个势阱，并且在
Figure PCTCN2020097106-appb-000015
处的势阱中存在两个量子态，这两个量子态的相位分布大部分限制在
Figure PCTCN2020097106-appb-000016
处的势阱范围内，即该两个量子态在
Figure PCTCN2020097106-appb-000017
处的势阱中的部分在该两个量子态中的占比均大于预设阈值，因此，可以选用这两个量子态作为逻辑比特进行编码。具体地，选用能量最小的量子态(图3B中虚线)表示逻辑“0”，选用能量次小的量子态(图3B中实线)表示逻辑“1”。
磁通控制模块3用于控制输入至量子比特结构1中的磁通量，以控制第一量子态和第二量子态之间的能级差，即控制第一量子态和第二量子态之间的跃迁频率。跃迁控制模块4用于控制输入至量子比特结构1中的微波脉冲，该微波脉冲的频率等于第一量子态与第二量子态之间的跃迁频率，从而控制量子比特结构1从第一量子态跃迁至第二量子态， 或者控制量子比特结构1从第二量子态跃迁至第一量子态。量子比特结构1中的量子态在第一量子态和第二量子态之间跃迁，读取模块5从量子比特结构1中读取到的量子态在第一量子态和第二量子态之间，并将读取到的量子态发送至编码模块2。
编码模块2利用量子比特结构1中的第一量子态和第二量子态作为逻辑比特进行编码。具体地，读取模块5读取量子比特结构1的量子态，并将读取到的量子态的能量值传输至编码模块2，当读取模块5读取到的量子态为第一量子态或第二量子态时，编码模块2根据读取模块5读取到的量子态的能量值生成相应的编码。以第一量子态的能量低于第二量子态的能量为例，则第一量子态对应逻辑比特“0”，第二量子态对应逻辑比特“1”，当量子比特结构1处于第一量子态时，编码模块2产生编码“0”，当跃迁控制模块4控制量子比特结构1由第一量子态跃迁至第二量子态时，编码模块2产生编码“1”。
本实施例中的量子比特在第一量子态和第二量子态之间跃迁，其跃迁的过程中相位中心改变较小，为等离子体振荡跃迁(Plasmon transition)，因此，本实施例中的量子比特可以命名为Plasonium量子比特。以图3B所对应的量子比特结构1为例，对本实施例中的量子态编码装置的操控性能、噪声敏感度等进行分析。
量子比特结构1的非简谐性与外加磁通Φ ext相关。图3B示出的结构中，外加磁通为0处的非简谐性最小，约为650MHz，最大可达1.5GHz。现有技术中广泛应用的Transmon量子比特的非简谐性约为200MHz-250MHz。基于此可知，本实施例中量子比特的非简谐性为Transmon量子比特的3倍以上，由此，本实施例中量子比特的操控速度至少为Transmon量子比特的3倍，具有更快的操控速度。
图3B示出的结构中，量子比特的电荷跃迁矩阵元
Figure PCTCN2020097106-appb-000018
为0.6-0.7，由此，可以通过电容耦合的方式实现单比特操控与多比特耦合。图3B示出的结构中，量子比特跃迁频率与外加磁通的关系如图4A所示。参阅图4A，可以看出，本实施例中的跃迁频率至少可以实现700MHz的调节。进一步地，参阅图4B，图4B示出了三种不同量子比特的磁通噪 声敏感度与跃迁频率调整大小之间的关系，可以看出，跃迁频率的大小变化相同时，本实施例中量子比特的频率对外加磁通的敏感度最小，由此，该量子态编码装置可以在调整跃迁频率的同时，保持较低的磁通噪声敏感度。
本公开另一实施例提供了一种利用上述图1-图4B所示实施例中的量子态编码装置进行编码的方法，方法包括：选取量子比特结构1中的第一量子态和第二量子态作为计算基矢进行编码。
图5示意性示出了本公开实施例提供的量子态编码装置进行编码的方法的流程图。具体地，参阅图5，该量子态编码装置进行编码的方法中，选取量子比特结构1中的第一量子态和第二量子态作为计算基矢进行编码的操作包括操作S510-S530。
在操作S510中，利用磁通控制模块3控制第一量子态和第二量子态之间的能级差。具体地，利用磁通控制模块3控制输入至量子比特结构1中的磁通量，从而控制第一量子态和第二量子态之间的能级差。
在操作S520中，利用跃迁控制模块4控制量子比特结构1中的量子态在第一量子态和第二量子态之间跃迁。具体地，利用跃迁控制模块4控制输入至量子比特结构1中的微波脉冲，从而控制量子比特结构1从第一量子态跃迁至第二量子态，或者控制量子比特结构1从第二量子态跃迁至第一量子态。
在操作S530中，编码模块2获取量子比特结构1中的量子态，并根据量子比特结构1中的第一量子态和第二量子态进行编码。具体地，编码模块2通过读取模块5读取量子比特结构1中的量子态，并根据读取到的量子态生成相应的编码“0”或“1”。
本实施例中未尽之细节，请参阅上述图1-图4B所示实施例中的量子态编码装置的描述，此处不再赘述。
图6示意性示出了本公开实施例提供的量子处理器的结构示意图。该量子处理器包括如上述图1-图4B所示实施例中的量子态编码装置。
量子处理器由K个量子态编码装置组成，K＞1。参阅图6，图中阴影部分为二维平面上的超导体，无阴影部分为未附着超导体的介电层。 具体地，量子处理器包含K个量子比特结构1、K个磁通控制模块3、K个跃迁控制模块4和K个读取模块5，量子比特结构1、磁通控制模块3、跃迁控制模块4和读取模块5一一对应，这K个量子比特结构1之间通过电容结构11耦合在一起。磁通控制模块3例如为一根低频微波传输线，作为磁通控制线，用于调节量子比特结构1的跃迁频率，并实现相位门等操作。跃迁控制模块4例如为一根高频微波传输线，作为跃迁控制线，以控制量子比特结构1的量子态在第一量子态和第二量子态之间跃迁。读取模块5例如为线性谐振腔，线性谐振腔与量子比特结构1相耦合，并利用色散测量的方式读取量子比特结构1的量子态。该量子处理器与现有的配套设备和系统具有很强的兼容性，便于今后大规模应用。
本实施例中未尽之细节，请参阅上述图1-图4B所示实施例中的量子态编码装置的描述，此处不再赘述。
以上所述的具体实施例，对本发明的目的、技术方案和有益效果进行了进一步详细说明，所应理解的是，以上所述仅为本发明的具体实施例而已，并不用于限制本发明，凡在本发明的精神和原则之内，所做的任何修改、等同替换、改进等，均应包含在本发明的保护范围之内。

Claims (10)

  1. 一种量子态编码装置，其特征在于，所述装置包括：
    量子比特结构(1)，在相位空间中具有N个势阱，第一势阱为所述N个势阱中能量最低的势阱，所述第一势阱中存在M个量子态，N为大于0的整数，M为大于1的整数；
    编码模块(2)，利用第一量子态和第二量子态作为逻辑比特进行编码，所述第一量子态和第二量子态为所述M个量子态中能量最低的两个量子态。
  2. 根据权利要求1所述的量子态编码装置，其特征在于，所述第一量子态在相位空间中在第一势阱中的分布比例、所述第二量子态在相位空间中在第一势阱中的分布比例均不小于预设阈值。
  3. 根据权利要求1所述的量子态编码装置，其特征在于，所述装置还包括：
    磁通控制模块(3)，用于控制输入至所述量子比特结构(1)中的磁通量，以控制所述第一量子态和第二量子态之间的能级差。
  4. 根据权利要求1所述的量子态编码装置，其特征在于，所述装置还包括：
    跃迁控制模块(4)，用于控制输入至所述量子比特结构(1)中的微波脉冲，以控制所述量子比特结构(1)在所述第一量子态与第二量子态之间跃迁。
  5. 根据权利要求1所述的量子态编码装置，其特征在于，所述量子比特结构(1)由电容结构(11)、约瑟夫森结结构(12)和电感结构(13)并联组成。
  6. 根据权利要求5所述的量子态编码装置，其特征在于，所述电感结构(13)由多个大约瑟夫森结串联或者由多个电感并联组成，所述电容结构(11)由多个电容并联组成，所述约瑟夫森结结构(12)由多个约瑟夫森结并联组成。
  7. 根据权利要求1所述的量子态编码装置，其特征在于，所述装 置还包括：
    读取模块(5)，用于读取所述量子比特结构(1)的量子态，并将读取到的量子态传输至所述编码模块(2)。
  8. 一种如权利要求1-7任一项所述的量子态编码装置进行编码的方法，其特征在于，所述方法包括：
    选取量子比特结构(1)中的第一量子态和第二量子态作为计算基矢进行编码。
  9. 根据权利要求8所述的方法，其特征在于，所述选取量子比特结构(1)中的第一量子态和第二量子态作为计算基矢进行编码，包括：
    利用磁通控制模块(3)控制所述第一量子态和第二量子态之间的能级差；
    利用跃迁控制模块(4)控制量子比特结构(1)中的量子态在第一量子态和第二量子态之间跃迁；
    利用编码模块(2)获取所述量子比特结构(1)中的量子态，并根据所述量子比特结构(1)中的第一量子态和第二量子态进行编码。
  10. 一种量子处理器，其特征在于，所述量子处理器包括如权利要求1-7任一项所述的量子态编码装置。
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