Using a D-Wave System

To use a D-Wave system as your solver (the compute resource for solving problems), you access it through the D-Wave Solver API (SAPI).

Interacting with SAPI

SAPI is an application layer built to provide resource discovery, permissions, and scheduling for quantum annealing resources at D-Wave. The requisite information for problem submission through SAPI includes:

  1. API endpoint URL

    A URL to the remote D-Wave system.

  2. API Token

    An authentication token the D-Wave system uses to authenticate the client session when you connect to the remote environment. Because tokens provide authentication, user names and passwords are not required in your code.

  3. Solver

    Name of the D-Wave resource to be used to solve your submitted problems.

You can find all the above information when you log in to your D-Wave account.

You save your SAPI configuration (URL, API token, etc) in a D-Wave Cloud Client configuration file that Ocean tools use unless overridden explicitly or with environment variables. Your configuration file can include one or more solvers.

Configuring a D-Wave System as a Solver

The simplest way to configure a solver is to use the dwave-cloud-client interactive CLI, which is installed as part of the dwave-ocean-sdk (or D-Wave Cloud Client tool installation).

  1. In the virtual environment you created as part of Installing Ocean Tools, run the dwave config create command (the output shown below includes the interactive prompts and placeholder replies).
$ dwave config create
Configuration file not found; the default location is: C:\\Users\\jane\\AppData\\Local\\dwavesystem\\dwave\\dwave.conf
Confirm configuration file path (editable):
Profile (create new): prod
API endpoint URL (editable): https://my.dwavesys.url/
Authentication token (editable): ABC-1234567890abcdef1234567890abcdef
Client class (qpu or sw): qpu
Solver (can be left blank): My_DWAVE_2000Q
Proxy URL (can be left blank):
Configuration saved.
  1. Enter the SAPI information (API URL and token) found when you log in to your D-Wave account. You can accept the command’s defaults and in the future update the file if needed.

Alternatively, you can create and edit a D-Wave Cloud Client configuration file manually or set the solver, API token, and URL directly in your code or as local environment variables. For more information, see the examples in this document or D-Wave Cloud Client.

Verifying Your Solver Configuration

You can test that your solver is configured correctly and that you have access to a D-Wave solver with the same dwave-cloud-client interactive CLI installed as part of the SDK or D-Wave Cloud Client tool installation.

  1. In your virtual environment, run the dwave ping command (the output shown below is illustrative only).
$ dwave ping
Using endpoint: https://my.dwavesys.url/
Using solver: My_DWAVE_2000Q

Wall clock time:
 * Solver definition fetch: 2007.239 ms
 * Problem submit and results fetch: 1033.931 ms
 * Total: 3041.171 ms

QPU timing:
 * total_real_time = 10493 us
 * anneal_time_per_run = 20 us
 * post_processing_overhead_time = 128 us
 * qpu_anneal_time_per_sample = 20 us
 # Snipped for brevity
  1. Optionally, run the dwave sample --random-problem command to submit a random problem to your configured solver (the output shown below is illustrative only).
$ dwave sample --random-problem
Using endpoint: https://my.dwavesys.url/
Using solver: My_DWAVE_2000Q
Using qubit biases: {0: -1.0345257941434953, 1: -0.5795618633919246, 2: 0.9721956399428491, 3: 1....
Using qubit couplings: {(1634, 1638): 0.721736584181423, (587, 590): 0.9611623181258304, (642, 64...
Number of samples: 1
Samples: [[1, 1, -1, -1, -1, -1, 1, -1, -1, 1, -1, 1, 1, 1, -1, -1, -1, -1, -1, -1, -1, 1, 1, -1,...
Occurrences: [1]
Energies: [-2882.197791239335]

Querying Available Solvers

The dwave-cloud-client interactive CLI can also show you the available solvers, their parameters, and properties.

  1. Run the dwave solvers command (the output shown below is illustrative only).
$ dwave solvers
Solver: My_DWAVE_2000Q
   Parameters:
      anneal_offsets: A list of anneal offsets for each working qubit (NaN if u...
      anneal_schedule: A piecewise linear annealing schedule specified by a list...
      annealing_time: A positive integer that sets the duration (in microsecond...

      <Output snipped for brevity>

   Properties:
      anneal_offset_ranges: [[-0.18627387668142237, 0.09542224439071689], [-0.1836548...
      anneal_offset_step: 0.00426679499507194
      anneal_offset_step_phi0: 0.0002716837027763096
      annealing_time_range: [1, 150000]
      chip_id: W7-1_C16_4724854-02-G4_C5R9-device-cal-data-18-05-27-14:27
      couplers: [[0, 4], [1, 4], [2, 4], [3, 4], [0, 5], [1, 5], [2, 5], ...

      <Output snipped for brevity>

Alternatively, from within your code or a Python interpreter you can query solvers available for a SAPI URL and API token using dwave-cloud-client Client.get_solvers() function. For example, the code below queries available solvers for your default SAPI URL and a specified token.

>>> from dwave.cloud import Client
>>> client = Client.from_config(token='ABC-123456789123456789123456789')
>>> client.get_solvers()
{u'2000Q_ONLINE_SOLVER1': <dwave.cloud.solver.Solver at 0x7e84fd0>,
 u'2000Q_ONLINE_SOLVER2': <dwave.cloud.solver.Solver at 0x7e84828>}

Typically, once you have selected and configured a solver, your code queries its parameters and properties as attributes of the instantiated solver object. The code example below sets a D-Wave system as the sampler, using the default SAPI configuration as set above, and queries its parameters.

>>> from dwave.system.samplers import DWaveSampler
>>> sampler = DWaveSampler()
>>> sampler.parameters
{u'anneal_offsets': ['parameters'],
u'anneal_schedule': ['parameters'],
u'annealing_time': ['parameters'],
u'answer_mode': ['parameters'],
u'auto_scale': ['parameters'],
# Snipped above response for brevity

Descriptions of D-Wave system parameters and properties are in the D-Wave system documentation.

Submitting Problems to a D-Wave System

Once you have configured a D-Wave Cloud Client configuration file your default solver configuration is used when you submit a problem without explicitly overriding it. For example, the following code uses a dwave-system structured sampler, EmbeddingComposite(DWaveSampler()), as the sampler, which uses a D-Wave system for the compute resource. Because no parameters (e.g., SAPI endpoint URL) are set explicitly, the line sampler = EmbeddingComposite(DWaveSampler()) uses your default solver.

>>> from dwave.system.samplers import DWaveSampler
>>> from dwave.system.composites import EmbeddingComposite
>>> sampler = EmbeddingComposite(DWaveSampler())
>>> response = sampler.sample_ising({'a': -0.5, 'b': 1.0}, {('a', 'b'): -1})
>>> response.data_vectors['energy']       
array([-1.5])

The examples under Getting Started demonstrate solving problems on the D-Wave system, starting from very simple and gradually increasing the complexity.