# Leap’s Hybrid Solvers¶

Note

Leap’s quantum-classical hybrid solvers are intended to solve arbitrary application problems formulated as binary quadratic models (BQM).

These solvers, which implement state-of-the-art classical algorithms together with intelligent allocation of the quantum processing unit (QPU) to parts of the problem where it benefits most, are designed to accommodate even very large problems. Leap’s solvers can relieve you of the burden of any current and future development and optimization of hybrid algorithms that best solve your problem.

These solvers have the following characteristics:

• There is no fixed problem structure. In particular, these solvers do not have properties num_qubits, qubits, and couplers.
• Only one solution is returned and it is not guaranteed to be optimal.
• Solver properties and parameters are entirely disjoint from those of other solvers.

## Generally Available Solvers¶

The generally available hybrid solvers depend on your Leap™ account. Check your Leap dashboard to see which hybrid solvers are available to you.

## Properties¶

This section describes the properties of Leap‘s solvers, in alphabetical order.

### category¶

Type of solver. Hybrid solvers support the following categories:

• hybrid—quantum-classical hybrid; typically one or more classical algorithms run on the problem while outsourcing to a quantum processing unit (QPU) parts of the problem where it benefits most.

### maximum_number_of_variables¶

Maximum number of problem variables accepted by the solver.

### minimum_time_limit¶

Minimum required run time, in seconds, the solver must be allowed to work on the given problem. Specifies the minimum time required for the number of problem variables, as a piecewise-linear curve defined by a set of floating-point pairs. The first element in each pair is the number of problem variables; the second is the minimum required time. The minimum time for any particular number of variables is a linear interpolation calculated on two pairs that represent the relevant range for the given number of variables. For example, if minimum_time_limit for a hybrid solver were [[1, 0.1], [100, 10.0], [1000, 20.0]], then the minimum time for a 50-variable problem would be 5 seconds, the linear interpolation of the first two pairs that represent problems with between 1 to 100 variables.

### maximum_time_limit_hrs¶

Maximum allowed run time, in hours, that can be specified for the solver.

### quota_conversion_rate¶

Ratio of time charged to Leap account quotas between QPU and hybrid solver usage. For example, for a value of 20, using 20 seconds of hybrid solver time is has an equivalent cost to using 1 second of QPU time.

### supported_problem_types¶

Indicates what problem types are supported for the solver. Hybrid solvers support the following energy-minimization problem types:

• bqm—binary quadratic model (BQM) problems; use $0/1$-valued variables and $-1/1$-valued variables.

## Parameters¶

This section describes the parameters accepted by Leap‘ s hybrid solvers, in alphabetical order. See Summary of Hybrid Solver Parameters for a summary and for the default values.

### time_limit¶

Specifies the maximum run time, in seconds, the solver is allowed to work on the given problem. Can be a float or integer in the range defined by minimum_time_limit for the problem’s number of variables.

## Summary of Hybrid Solver Parameters¶

Hybrid solver parameters and their default values are summarized in the table below.

Table 1 Hybrid Solver Parameters
Parameter Range Default Value
time_limit See minimum_time_limit Problem dependent