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Comparators

The following comparators are supported:

  • GreaterThan (denoted as '>')
  • GreaterEqual (denoted as '>=')
  • LessThan (denoted as '<')
  • LessEqual (denoted as '<=')
  • NotEqual (denoted as '!=')
  • Equal (denoted as '==')

Note that integer and fixed-point numbers are represented in a 2-complement method during function evaluation. The binary number is extended in the case of a register size miss-match. For example, the positive signed number \((110)_2=6\) is expressed as \((00110)_2\) when operating with a 5-qubit register. Similarly, the negative signed number \((110)_2=-2\) is expressed as \((11110)_2\).

Examples:

(5 <= 3) = 0

(5 == 5) = 1

(\((011)_2\) == \((11)_2\)) = 1

(signed \((101)_2\) < unsigned \((101)_2\)) = 1

Syntax

Function: Equal/NotEqual/GreaterThan/GreaterEqual/LessThan/LessEqual

Parameters:

{
  "function": "Equal",
  "function_params": {
    "left_arg": 3,
    "right_arg": {
      "size": 3
    }
  }
}

Register Names

By default, the input registers are called left_arg and right_arg. If the name field of a RegisterUserInput object is specified, then the name of the register is determined accordingly. If one of the arguments is a constant then it is not available as an input register.

The output registers include the result register. By default, its name is determined by the specific comparator used: is_equal, is_less_than, etc. It may be overridden by the output_name argument. In addition, the input registers are also available as output registers, with the same names.

Example 1: Two Register

{
  "logic_flow": [
    {
      "function": "Equal",
      "function_params": {
        "left_arg": {
          "size": 5,
          "is_signed": true
        },
        "right_arg": {
          "size": 3
        }
      }
    }
  ]
}

from classiq import Model, QUInt, QSInt
from classiq.builtin_functions import Equal

params = Equal(
    left_arg=QSInt(size=5).to_register_user_input(),
    right_arg=QUInt(size=3).to_register_user_input(),
)
model = Model()
model.Equal(params)
circuit = model.synthesize()

This example generates a circuit that performs 'equal' between two registers. The left arg is a signed register with 5 qubits and the right arg is an unsigned register with 3 qubits.

img_11.png

Example 2: Integer and Register

{
  "logic_flow": [
    {
      "function": "Equal",
      "function_params": {
        "left_arg": 3,
        "right_arg": {
          "size": 3
        }
      }
    }
  ]
}

from classiq import Model, RegisterUserInput
from classiq.builtin_functions import Equal

params = Equal(left_arg=3, right_arg=RegisterUserInput(size=3))
model = Model()
model.Equal(params)
circuit = model.synthesize()

This example generates a circuit that performs 'equal' between a quantum register and an integer. The left arg is an integer equal to three and the right arg is an unsigned quantum register with 3 qubits.

img_12.png