How To Implement Dwave Qbsolve In Python? – TechDharm


How To Implement Dwave Qbsolve In Python

A rapidly developing technology called quantum computing has the power to change the way we handle complex issues completely. D-Wave, one of the industry’s top businesses, has created a quantum computer that can complete some optimization tasks far more quickly than traditional computers. In this post, we’ll look at how to use Python to build DWave’s qbsolve program, which enables you to use the quantum computer’s capability to solve optimization issues.

What is qbsolve?

Qbsolve is a software package developed by D-Wave that allows users to solve optimization problems using D-Wave’s quantum computer. It takes a quadratic unconstrained binary optimization (QUBO) problem as input, a particular optimization problem where the variables can only take on binary values (0 or 1). Qbsolve then uses D-Wave’s quantum computer to find the optimal solution to the problem.

Qbsolve can be used for many optimization problems, including those that arise in machine learning, cryptography, and logistics. It is a useful tool for both researchers and practitioners because to its speed and precision.

Installing Qbsolve: 

Installing qbsolve is necessary before using it. Qbsolve can be installed using pip, a package installer for Python. Here’s how to do it:

  • 1. Open a terminal or command prompt.
  • 2. Type “pip install dwave-qbsolve” and press enter.
  • 3. Hold off until the installation is finished.
  • 4. Once qbsolve is installed, we can use it to solve optimization problems.

Using Qbsolve:

To use qbsolve, we need to define a QUBO problem. Start with a simple illustration. If we wish to get the function’s minimal value, f(x) = x1 + 2×2 – x1x2. We can express this as a QUBO problem by defining a matrix Q whose elements represent the coefficients of the variables and their interactions. In this case, we have:

Q = [[1, -1],

[-1, 2]]

The diagonal elements represent the variables’ coefficients (in this case, x1 and x2). The off-diagonal components represent the coefficients of the interaction between the variables (in this case, -1 represents the coefficient of x1x2).

We can then pass this matrix to qbsolve to find the optimal x1 and x2 that minimize f(x). Here’s the code to do this:


import dwave_qbsolve as qbs

Q = [[1, -1], 

     [-1, 2]]

response = qbs.QBSolv().sample_qubo(Q)


This code defines and passes the matrix Q to qbsolve using the sample_qubo function. The response object contains the optimal values of x1 and x2 that minimize f(x). When we print the response, we get the following output:


[{‘0’: 1, ‘1’: 0, ‘energy’: -1.0, ‘num_occurrences’: 1}, {‘0’: 0, ‘1’: 0, ‘energy’: 0.0, ‘num_occurrences’: 1}, {‘0’: 1, ‘1’: 1, ‘energy’: 2.0, ‘num_occurrences’: 1}]

This output contains four dictionaries, each representing a possible solution to the problem. The keys in each dictionary represent the values of x1 and x2 (0 or 1) that minimize the function f(x). The “num occurrences” key denotes the number of times that solution was discovered, and the “energy” key indicates the value of f(x) for that specific solution.

In this situation, the best possible outcomes are x1=1 and x2=0, respectively, both of which result in a minimum value of f(x)=-1. The other two solutions (x1=0, x2=0 and x1=1, x2=1) give f(x) values higher.

Of course, this is an elementary example, and QUBO problems can be much more complex in practice. However, the basic approach is the same: define the matrix Q representing the problem, pass it to qbsolve, and interpret the results to find the optimal solution.

Working With Qbsolve Parameters

The behavior of the solver may be controlled using a variety of options in Qbsolve. These include:

  • num_repeats: the number of times to repeat the solving process.
  • Target: the target energy to aim for. If specified, the solver will attempt to find a solution with a power lower than the target.
  • Timeout: the maximum time to spend on solving in seconds.

These parameters can be specified when calling the sample_qubo function. For example:


response = qbs.QBSolv().sample_qubo(Q, num_repeats=10, target=-1, timeout=60)

This code sets the number of repeats to 10, the target energy to -1, and the timeout to 60 seconds. It’s recommended testing to discover the ideal values for your problem because changing these parameters might impact the effectiveness and speed of the solutions provided.


Qbsolve offers a robust and accessible solution for solving optimization problems through quantum computing.  As quantum computing continues to develop, qbsolve and similar tools will undoubtedly become increasingly valuable in a wide range of applications and industries.

Qbsolve: Frequently Asked Questions (FAQs)

Q1. What is qbsolve?

A: Qbsolve is a software package developed by D-Wave that can solve optimization problems using D-Wave’s quantum computer.

Q2. Do I need a D-Wave quantum computer to use qbsolve?

A: No, qbsolve can be used on any computer, regardless of whether it has access to a quantum computer. It can simulate the behavior of a quantum computer using classical computing resources.

Q3. What kind of problems can be solved using qbsolve?

A: Qbsolve can solve optimization problems expressed as a quadratic unconstrained binary optimization (QUBO) problem.

Q4. What is a QUBO problem?

A: A QUBO problem is an optimization problem where the objective function is expressed as a quadratic equation in binary variables (variables that can only take the values 0 or 1) subject to some constraints.

Q5. How do I install qbsolve?

A: You can install qbsolve using pip, the Python package manager. Execute this terminal command: pip install dwave-qbsolv

Q6. Can I control the behavior of qbsolve?

A: Yes, qbsolve has several parameters that can be used to control its behavior, such as the number of repeats, target energy, and timeout.

Q7. How accurate are the results obtained using qbsolve?

A: The accuracy of the answers produced by qbsolve relies on various variables, including the difficulty of the problem and the number of repeats. The results obtained using qbsolve can provide a reasonable estimate of the optimal solution, but they may not be exact due to the limitations of classical computing resources.

Q8. Are there any alternative software packages to qbsolve for solving QUBO problems?

A: Yes, there are several other software packages available for solving QUBO problems, such as dimod, neal, and pyqubo.

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