---
title: C1Register (latest version)
description: API reference for samplomatic.virtual_registers.C1Register in the latest version of samplomatic
source: https://quantum.cloud.ibm.com/docs/en/api/samplomatic/auto/virtual-registers-c-1-register
---

# C1Register

*class* `samplomatic.virtual_registers.C1Register(virtual_gates: ndarray)`

[GitHub](https://github.com/Qiskit/samplomatic/tree/main/samplomatic/virtual_registers/c1_register.py#L38-L87)

Bases: `FiniteGroupRegister`

Virtual register of C1 gates.

Here, we use an integer representation constructed from flattening the six cosets of the Pauli subgroup and the subgroup itself. Concretely, a value $c$ corresponds to the unitary $G^i H^j P(k)$ where $k = c % 4, j = c // 4 % 2, i = c // 8 % 3$ and $G = HS$.

**Attributes Summary**

|                                                                                                                                                 |                                                                                                                                                   |
| ----------------------------------------------------------------------------------------------------------------------------------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------- |
| [`CONVERTABLE_TYPES`](#samplomatic.virtual_registers.C1Register.CONVERTABLE_TYPES "samplomatic.virtual_registers.C1Register.CONVERTABLE_TYPES") | Valid arguments for [`convert_to()`](#samplomatic.virtual_registers.C1Register.convert_to "samplomatic.virtual_registers.C1Register.convert_to"). |
| [`GATE_SHAPE`](#samplomatic.virtual_registers.C1Register.GATE_SHAPE "samplomatic.virtual_registers.C1Register.GATE_SHAPE")                      | The array shape of any single virtual gate.                                                                                                       |
| [`SUBSYSTEM_SIZE`](#samplomatic.virtual_registers.C1Register.SUBSYSTEM_SIZE "samplomatic.virtual_registers.C1Register.SUBSYSTEM_SIZE")          | The number of qubits each virtual gate acts on.                                                                                                   |
| [`TYPE`](#samplomatic.virtual_registers.C1Register.TYPE "samplomatic.virtual_registers.C1Register.TYPE")                                        | The group name in 1-1 correspondence with this virtual gate type.                                                                                 |
| [`inverse_table`](#samplomatic.virtual_registers.C1Register.inverse_table "samplomatic.virtual_registers.C1Register.inverse_table")             | The lookup table for the inverse.                                                                                                                 |
| [`lookup_table`](#samplomatic.virtual_registers.C1Register.lookup_table "samplomatic.virtual_registers.C1Register.lookup_table")                | The lookup table for the group operation.                                                                                                         |

**Methods Summary**

|                                                                                                                                                     |                                                             |
| --------------------------------------------------------------------------------------------------------------------------------------------------- | ----------------------------------------------------------- |
| [`convert_to`](#samplomatic.virtual_registers.C1Register.convert_to "samplomatic.virtual_registers.C1Register.convert_to")(register\_type)          | Convert this register type to some other type, if possible. |
| [`from_tableau`](#samplomatic.virtual_registers.C1Register.from_tableau "samplomatic.virtual_registers.C1Register.from_tableau")(tableaus)          | Return a new register from an array of tableaus.            |
| [`identity`](#samplomatic.virtual_registers.C1Register.identity "samplomatic.virtual_registers.C1Register.identity")(num\_subsystems, num\_samples) | Instantiate a new register of identity virtual gates.       |
| [`to_tableau`](#samplomatic.virtual_registers.C1Register.to_tableau "samplomatic.virtual_registers.C1Register.to_tableau")()                        | Return an array of tableaus with the same shape as this.    |

**Attributes Documentation**

### CONVERTABLE\_TYPES

Type: [`frozenset`](https://docs.python.org/3/builtins/stdtypes.html#frozenset)\[[`VirtualType`](/docs/api/samplomatic/auto/virtual-registers-virtual-type "samplomatic.virtual_registers.virtual_type.VirtualType")]

Default value: `frozenset({VirtualType.C1, VirtualType.U2})`

Valid arguments for [`convert_to()`](#samplomatic.virtual_registers.C1Register.convert_to "samplomatic.virtual_registers.C1Register.convert_to").

### GATE\_SHAPE

Type: [`tuple`](https://docs.python.org/3/builtins/stdtypes.html#tuple)\[[`int`](https://docs.python.org/3/builtins/functions.html#int), ...]

Default value: `()`

The array shape of any single virtual gate.

### SUBSYSTEM\_SIZE

Type: [`int`](https://docs.python.org/3/builtins/functions.html#int)

Default value: `1`

The number of qubits each virtual gate acts on.

### TYPE

Type: [`VirtualType`](/docs/api/samplomatic/auto/virtual-registers-virtual-type "samplomatic.virtual_registers.virtual_type.VirtualType")

Default value: `'c1'`

The group name in 1-1 correspondence with this virtual gate type.

### inverse\_table

### lookup\_table

**Methods Documentation**

### convert\_to

`convert_to(register_type)`

[GitHub](https://github.com/Qiskit/samplomatic/tree/main/samplomatic/virtual_registers/c1_register.py#L60-L63)

Convert this register type to some other type, if possible.

**Parameters**

**register\_type** – The type of register to convert to.

**Returns**

A new register of the specified output type, or this instance if its type is `register_type`.

**Raises**

[**VirtualGateError**](/docs/api/samplomatic/auto/exceptions-virtual-gate-error "samplomatic.exceptions.VirtualGateError") – If this type cannot be converted to the specified type.

### from\_tableau

*classmethod* `from_tableau(tableaus: _Buffer | _SupportsArray[dtype[Any]] | _NestedSequence[_SupportsArray[dtype[Any]]] | complex | bytes | str | _NestedSequence[complex | bytes | str]) → C1Register`

[GitHub](https://github.com/Qiskit/samplomatic/tree/main/samplomatic/virtual_registers/c1_register.py#L69-L79)

Return a new register from an array of tableaus.

**Parameters**

**tableaus** – The tableaus corresponding the registers.

**Returns**

A virtual register in the enumerated representation.

### identity

*classmethod* `identity(num_subsystems, num_samples)`

[GitHub](https://github.com/Qiskit/samplomatic/tree/main/samplomatic/virtual_registers/c1_register.py#L65-L67)

Instantiate a new register of identity virtual gates.

### to\_tableau

`to_tableau() → ndarray`

[GitHub](https://github.com/Qiskit/samplomatic/tree/main/samplomatic/virtual_registers/c1_register.py#L81-L87)

Return an array of tableaus with the same shape as this.

**Returns**

An array of tableaus.