Oscillator ising machine with linear coupling

Abstract

An oscillator Ising machine with linear coupling comprises a pair of ring oscillators with the same structure and equipped with oscillator replica units and a coupling unit, wherein the two sides of the coupling unit are connected with the ring oscillators and the corresponding oscillator replica units. In the present application, the interaction strength and sign between oscillators are completely determined by the control word and the switch state, without any transconductance amplifier, bias current or active feedback circuit. At the same time, high linearity coupling adjustment is realized under the premise of maintaining full passive characteristics, and the coupling conductance and the control code have a strict linear relationship. High-precision coupling matrix mapping can be realized under the conditions of pure passivity, linear adjustment and differential symmetry.

Description

Technical Field

[0001] This invention relates to a technology in the field of physical computing circuits, specifically an Ising oscillator with linear coupling. Background Technology

[0002] Existing coupling networks for Ising machines mainly employ capacitor or transconductance active coupling circuits, multi-resistor segmented or switch array coupling circuits, or current mirror active coupling. However, existing technologies are limited by voltage linearity and bias stability. The number of adjustable coupling strengths is linearly related to the number of coupling capacitors. When the bit width is high, the number of resistors increases exponentially, the area and matching difficulty increase sharply, or the adjustment range is limited and additional static power consumption is introduced. Summary of the Invention

[0003] This invention addresses the shortcomings of existing technologies, such as the exponential growth of the resistive coupling network area with bit width, insufficient linearity, and unbalanced load. It proposes an Ising oscillator with linear coupling, which achieves true passive linear coupling while ensuring the stability of the oscillator's phase and frequency.

[0004] This invention is achieved through the following technical solution:

[0005] The present invention relates to an Ising oscillator with linear coupling, comprising: a pair of ring oscillators equipped with oscillator replication units and having identical relative configurations, and a coupling unit, wherein: the two sides of the coupling unit are respectively connected to the ring oscillators and their corresponding oscillator replication units.

[0006] The ring oscillator is composed of n+1 oscillation differential buffers connected end to end to generate an oscillation signal. The output terminal of the (n+1)th stage oscillation differential buffer serves as the nth stage differential output terminal of the oscillator and is connected to the coupling unit and the first stage oscillation differential buffer respectively to output a coupling voltage. The output terminal of the nth stage oscillation differential buffer is connected to the input terminal of the oscillator replication unit.

[0007] The oscillator replication unit consists of two replication differential buffers connected end-to-end. The input of the first-stage replication differential buffer is connected to the output of the nth-stage oscillation differential buffer in the ring oscillator, and its output is connected to the input of the second-stage replication differential buffer and the coupling unit, respectively, and outputs a replication voltage.

[0008] The coupling unit includes: a symbol switching switch and four R-2R resistor networks respectively disposed at its two ends for establishing adjustable conductance connections, wherein: the input terminal of the first R-2R resistor network located on the side of the symbol switching switch is connected to the non-inverting output terminal of the nth stage oscillation differential buffer of the ring oscillator and the first stage replication differential buffer of the oscillator replication unit, respectively; the input terminal of the second R-2R resistor network on the same side is connected to the inverting output terminal of the nth stage oscillation differential buffer of the ring oscillator and the first stage replication differential buffer of the oscillator replication unit, respectively; and the third and fourth R-2R resistor networks on opposite sides are connected in the same way.

[0009] The symbol switching switch SW is a differential network consisting of four switches, used to control the connection mode of the differential terminals between a pair of ring oscillators to achieve switching of coupling polarity.

[0010] The R-2R resistor network is composed of several resistors with resistance values ​​of R and 2R connected in series, and contains K+1 levels of branches. Each branch node is equipped with a switch, and the conduction state of K+1 switches is controlled by a K-bit control word, thereby determining the flow direction of the K+1 branch current between a pair of differential terminals of the same name.

[0011] Technical effect

[0012] This invention employs a fully passive linear coupling structure composed of two R-2R resistor networks, achieving high-precision, scalable conductance adjustment through current flow distribution; and uses a differential sign switching switch to achieve coupling polarity reversal. Through two identical LSB weights and a normalized current distribution design, the conductance resolution and bit width expand linearly, while the area and power consumption increase only linearly. The differential sign switching switch enables positive and negative coupling reversal, directly mapping the positive and negative interactions in the Ising model. A load balancing switch is incorporated to maintain constant load capacitance at the Vcouple and Vreplica nodes under different coupling states, significantly reducing oscillation phase drift caused by load imbalance. Compared to existing technologies, the interaction strength and sign between the oscillators in this invention are entirely determined by the control word and switch state, achieving high-linearity coupling adjustment while maintaining fully passive characteristics without any transconductance amplifiers, bias currents, or active feedback circuits. The coupling conductance and control code exhibit a strictly linear relationship; high-precision coupling matrix mapping can be achieved under purely passive, linearly adjustable, and differentially symmetrical conditions. Compared with traditional coupling methods using active transconductance, capacitor, or current mirror structures, this invention achieves: no static bias current, no DC power consumption; high equivalent conductor linearity; and linear growth in area and number of resistors as the bit width expands. Therefore, the linear coupling structure proposed in this invention provides a new circuit foundation for the high-precision mapping and scalable implementation of the Ising oscillator. Attached Figure Description

[0013] Figure 1 This is a schematic diagram of the structure of the present invention;

[0014] Figure 2 This is a schematic diagram of the oscillator and oscillator replication unit of the present invention;

[0015] Figure 3 This is a schematic diagram illustrating the effect of an embodiment of the present invention applied to a coupling unit of a 6-bit coupled control word. Detailed Implementation

[0016] like Figure 1 As shown, this embodiment relates to an Ising oscillator with linear coupling, comprising: a pair of ring oscillators O1 and O2 with oscillator replication units having the same relative arrangement structure, and a coupling unit C, wherein: the two sides of the coupling unit C are respectively connected to the ring oscillator and its corresponding oscillator replication unit.

[0017] like Figure 2 As shown, the ring oscillator is composed of n+1 oscillation differential buffers connected end to end to generate an oscillation signal. The output terminal of the (n+1)th stage oscillation differential buffer serves as the nth stage differential output terminal of the oscillator and is connected to the coupling unit and the first stage oscillation differential buffer respectively, outputting a coupling voltage Vcouple. The output terminal of the nth stage oscillation differential buffer is connected to the input terminal of the oscillator replication unit.

[0018] In this embodiment, n=3.

[0019] The oscillator replication unit OR1 (OR2) consists of two replication differential buffers connected end to end. The input of the first-stage replication differential buffer is connected to the output of the nth-stage oscillation differential buffer in the ring oscillator, and the output is connected to the input of the second-stage replication differential buffer and the coupling unit, respectively, and outputs the replication voltage Vreplica.

[0020] The coupling unit includes: a symbol switching switch SW for controlling the symbols of O1 and O2 coupling, and four R-2R resistor networks RL1, RL2, RL3, and RL4 respectively disposed at its two ends for establishing adjustable conductance connections. The input terminal of the first R-2R resistor network RL1 located on the side of the symbol switching switch SW is connected to the non-inverting output terminal of the nth stage oscillation differential buffer of the ring oscillator O1 and the first stage replication differential buffer of the oscillator replication unit OR1. The input terminal of the second R-2R resistor network RL2 on the same side is connected to the inverting output terminal of the nth stage oscillation differential buffer of the ring oscillator O1 and the first stage replication differential buffer of the oscillator replication unit OR1. The third and fourth R-2R resistor networks on opposite sides are connected in the same way.

[0021] The symbol switching switch SW is a differential network composed of four switches, used to control the connection mode of the differential terminals between O1 and O2 to achieve the switching of coupling polarity.

[0022] like Figure 3 As shown, the R-2R resistor network is composed of several resistors with resistance values ​​of R and 2R connected in series, and contains K+1 levels of branches. Each branch node is equipped with a switch, and the conduction state of K+1 switches is controlled by a K-bit control word, thereby determining the flow direction of the K+1 branch current between a pair of differential terminals of the same name.

[0023] The specific flow direction is as follows: the first R-2R resistor network RL1 selects the direction of branch current flow between the non-inverting output terminal O1+ of the nth stage oscillation differential buffer of the ring oscillator O1 and the non-inverting output terminal OR1+ of the first stage replication differential buffer of the oscillator replication unit OR1; the second R-2R resistor network RL2 selects the direction of branch current flow between the inverting output terminal O1- of the nth stage oscillation differential buffer of the ring oscillator O1 and the inverting output terminal OR1- of the first stage replication differential buffer of the oscillator replication unit OR1; and the third R-2R resistor network RL3 selects the direction of branch current flow between the nth stage oscillation differential buffer of the ring oscillator O2 and ... second stage replication differential buffer OR1+ of the second stage replication differential buffer of the ring oscillator O2. The non-inverting output terminal O2+ of the differential buffer and the non-inverting output terminal OR2+ of the first-stage replica differential buffer of the oscillator replication unit OR2 select the direction of the branch current. The fourth R-2R resistor network RL4 selects the direction of the branch current between the inverting output terminal O2- of the nth-stage oscillation differential buffer of the ring oscillator O2 and the inverting output terminal OR2- of the first-stage replica differential buffer of the oscillator replication unit OR2. When the switch corresponding to a certain branch is closed, the branch current flows into the ring oscillator terminal (O±). When the switch of that stage is open, the branch current flows to the oscillator replication unit terminal (OR±).

[0024] In each R-2R resistor network, each bit of the control word corresponds to a set of differential switches. The control signals for the positive switches are denoted as b0', b0, b1, b2…b4, and the control signals for the negative switches are denoted as b0'¯, b0¯, b1¯, b2¯…b4¯. When a positive switch of a certain stage is closed, the branch current flows into the oscillator terminal O+; when the switch of that stage is open or the corresponding negative switch is closed, the branch current flows into the replication terminal OR+ (or…). When the symbol switching switch SW is in the first state, O1+ is connected to O2+. Connected, forming positive coupling When SW is in the second state, Connected and Connected, forming negative coupling In addition, the R-2R resistor network also includes a load balancing switch BP, and each differential terminal... Connected to two switches in the on state and two switches in the off state respectively, the equivalent resistance and capacitance distribution of each port under any control word remains constant, thereby maintaining the symmetry and frequency stability of the oscillator output when the coupling conductance changes.

[0025] The branch currents decrease in a binary weighted manner, each decreasing to half of the total current. k To ensure overall uniformity, the lowest two digits (the first and second digits) have the same weight, both being equal. The weights of the remaining i-th elements (3≤i≤K) are as follows: Therefore, the sum of all weights is 1. Thus, the equivalent conductance formed between the two terminals connected to any array can be expressed as a linear weighted superposition of the above weights, which varies strictly linearly and monotonically with the input control word across the entire code range.

[0026] like Figure 3 As shown, through practical application experiments, K equals 5 in this embodiment, i.e., a 6-bit coupling control word, of which 1 bit is the sign control word and 5 bits are the coupling strength control word. Using a resistor with a resistance value of 2R as the minimum area resistor unit, the number of minimum area resistor units required for a single R-2R resistor network RL1-RL4 in this embodiment is 14. Resistors with a resistance value of R are formed by connecting two minimum area resistor units in parallel. To achieve the same resistance and adjustable resistance range as the single R-2R resistor network RL1-RL4 in this embodiment, the number of minimum area resistor units required for the binary R network is 47. Resistors with a resistance value of 4R are formed by connecting two minimum area resistor units in series, resistors with a resistance value of 8R are formed by connecting four minimum area resistor units in series, and so on for the remaining resistors. The number of resistors required in this embodiment is reduced from 47 in the traditional binary arrangement to 14.

[0027] Compared to traditional K-bit coupling strength control methods, configuration is required. Compared to individual resistor elements, this invention, through a linear R-2R resistor network structure, only requires... The same conductivity resolution can be achieved with a single resistor, thus optimizing the number of resistors from an exponential relationship to a linear relationship, significantly reducing the area.

[0028] The above-described specific implementations can be partially adjusted by those skilled in the art in different ways without departing from the principles and purpose of the present invention. The scope of protection of the present invention is defined by the claims and is not limited to the above-described specific implementations. All implementation schemes within the scope of the claims are bound by the present invention.

Claims

1. An Ising oscillator with linear coupling, characterized in that, include: A pair of ring oscillators with oscillator replication units and a coupling unit with the same relative configuration structure, wherein: the two sides of the coupling unit are respectively connected to the ring oscillator and its corresponding oscillator replication unit, and the ring oscillator consists of n+1 oscillation differential buffers connected end to end; The oscillator replication unit consists of two replication differential buffers connected end to end. The input of the first-stage replication differential buffer is connected to the output of the nth-stage oscillation differential buffer in the ring oscillator, and the output is connected to the input of the second-stage replication differential buffer and the coupling unit to output the replication voltage. The coupling unit includes: a sign switching switch and four R-2R resistor networks respectively disposed at its two ends for establishing adjustable conductance connections, wherein: the input terminal of the first R-2R resistor network located on the side of the sign switching switch is connected to the non-inverting output terminal of the nth stage oscillation differential buffer of the ring oscillator and the first stage replication differential buffer of the oscillator replication unit, respectively; the input terminal of the second R-2R resistor network on the same side is connected to the inverting output terminal of the nth stage oscillation differential buffer of the ring oscillator and the first stage replication differential buffer of the oscillator replication unit, respectively; the connection method of the third and fourth R-2R resistor networks on opposite sides is the same. The R-2R resistor network is composed of several resistors with resistance values ​​of R and 2R connected in series, and contains K+1 levels of branches. Each branch node is equipped with a switch, and the conduction state of K+1 switches is controlled by a K-bit control word, thereby determining the flow direction of the K+1 branch current between a pair of differential terminals of the same name.

2. The Ising oscillator with linear coupling according to claim 1, characterized in that, The output of the (n+1)th stage oscillation differential buffer serves as the nth stage differential output of the oscillator, and is connected to the coupling unit and the first stage oscillation differential buffer respectively, outputting a coupling voltage. The output of the nth stage oscillation differential buffer is connected to the input of the oscillator replication unit.

3. The Ising oscillator with linear coupling according to claim 1, characterized in that, The symbol switching switch is a differential network consisting of four switches, used to control the connection mode of the differential terminals between a pair of ring oscillators to achieve switching of coupling polarity.

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