CHANGELOG.md

News

v0.7.1 - unreleased

• (breaking) Simulation, network, protocol, and visualization traces now use Julia's standard logging macros with stable event symbols and structured metadata. Rendered messages have changed, and routine low-level simulation and protocol control-flow records now use Debug severity in the LOG_GROUPS.protocol group. The @simlog macro and both non-public timestr methods were removed immediately; use simulation_log_context or ProtocolZoo.protocol_log_context with @debug, @warn, or @error.
• Additional visualization methods for states of registers.
• (fix) observable now locally composes separately factorized states, and pure Clifford states accept dense QuantumOptics observables.
• Package logs expose stable, filterable domain groups through LOG_GROUPS.
• Dense observables on pure Clifford states now warn before converting the entire stabilizer state to an exponentially sized ket, with the default logger showing the warning once per session. Mixed stabilizer states fail early with guidance to use representation-native Pauli observables.
• (fix) QuantumMCRepr slots now store pure trajectories in an internal MCKet wrapper, so background evolution selects Kraus sampling through structural dispatch. ConstantHamiltonianEvolution preserves the wrapper through Schrödinger or Monte Carlo wave-function evolution. Lindblad-only background updates now also preserve it through Monte Carlo wave-function evolution with a zero Hamiltonian. Partial trace now samples the discarded subsystem's canonical basis and preserves the conditional trajectory as an MCKet; its ensemble equals the exact partial trace. Grouped traceout! calls that delete every slot of a shared state skip backend reduction and RNG sampling entirely. stateref.state[] exposes the wrapper, and StateRef displays identify its implementation module as QuantumSavory.
• permits_virtual_edge now accepts protocol types as well as instances, so introspection code can query the capability without constructing protocols.
• (fix) Make the graph_builder examples independent of the arbitrary order of equal-cardinality matchings.
• (breaking) Named tag heads now subtype the exported AbstractTag marker. Custom types passed to EntanglerProt(...; tag=MyTag) or EntanglementConsumer(...; tag=MyTag) must be concrete and migrate to struct MyTag <: AbstractTag end. The entangler accepts nothing, while the consumer requires a named tag type. Generic Tag(DataType, ...) construction and querying remain unrestricted.
• RegisterNet now accepts (src, dst) -> delay callables for classical_delay and quantum_delay, enabling per-link and asymmetric transport delays while retaining scalar delay support.

v0.7.0 - 2026-06-12

• (breaking) (fix) The ProtocolZoo entanglement-tracking tags and messages now carry entanglement pair IDs, fixing a class of bookkeeping bugs (#303) where stale update messages could be applied to the wrong Bell pair after a physical slot was reused. See the porting guide below.
• (fix) EntanglementTracker no longer waits on the physical slot lock when an incoming update only needs EntanglementHistory metadata of an empty slot, fixing a race (#448) where valid in-flight updates were dropped as stale because history forwarding was serialized behind slot reuse by an EntanglerProt.
• SwapperProt gained a max_history_per_slot option and CutoffProt gained a max_delete_per_slot option, enforcing FIFO caps on accumulated EntanglementHistory and EntanglementDelete metadata. CutoffProt no longer deletes old EntanglementHistory tags itself; history cleanup is now owned by the swapper that creates those tags.
• Stale update/delete messages dropped by EntanglementTracker are now logged at @warn level instead of @error, as with pair IDs such drops are expected only under benign circumstances (e.g. history garbage collection).

Porting guide for the pair-ID tag schema

User code that creates, queries, or destructures the ProtocolZoo entanglement tags needs the following updates. The new ID fields are of type EntanglementID (an alias for Int), with NO_ENTANGLEMENT_ID == 0 reserved as the neutral/legacy value; fresh IDs are created with fresh_entanglement_id() and swap composition uses combine_entanglement_ids(a, b).

The tag schemas changed as follows (new fields in bold):

Tag	Old schema	New schema
EntanglementCounterpart	(remote_node, remote_slot)	(remote_node, remote_slot, pair_id)
EntanglementHistory	(remote_node, remote_slot, swap_remote_node, swap_remote_slot, swapped_local)	(remote_node, remote_slot, swap_remote_node, swap_remote_slot, swapped_local, local_chunk_id, swapped_chunk_id)
EntanglementUpdateX / EntanglementUpdateZ	(past_local_node, past_local_slot, past_remote_slot, new_remote_node, new_remote_slot, correction)	(target_pair_id, other_pair_id, past_local_node, past_local_slot, past_remote_slot, new_remote_node, new_remote_slot, correction)
EntanglementDelete	(send_node, send_slot, rec_node, rec_slot)	(target_pair_id, send_node, send_slot, rec_node, rec_slot)

Required changes, in decreasing order of likelihood that they affect you:

1. Queries must use the new arity. A query with the old number of fields silently matches nothing — it does not error. Add a wildcard for the new field(s), e.g.
   • query(reg, EntanglementCounterpart, node, ❓) → query(reg, EntanglementCounterpart, node, ❓, ❓)
   • queryall(reg, EntanglementHistory, ❓, ❓, ❓, ❓, ❓) → queryall(reg, EntanglementHistory, ❓, ❓, ❓, ❓, ❓, ❓, ❓)
   • querydelete!(mb, EntanglementUpdateX, ❓, ❓, ❓, ❓, ❓, ❓) → querydelete!(mb, EntanglementUpdateX, ❓, ❓, ❓, ❓, ❓, ❓, ❓, ❓)
2. Raw tag! and Tag calls must include the new fields. tag!(slot, EntanglementCounterpart, node, slot_idx) still runs, but creates an old-arity tag that is invisible to all queries and protocols in this release. Write tag!(slot, EntanglementCounterpart, node, slot_idx, pair_id) instead, where pair_id comes from fresh_entanglement_id() for a new pair (use the same ID on both ends of the pair), or NO_ENTANGLEMENT_ID for metadata that does not participate in ID-based tracking.
3. Positional destructuring of update/delete messages must shift indices. The two ID fields are prepended to EntanglementUpdateX/EntanglementUpdateZ and one ID field is prepended to EntanglementDelete, so e.g. tag[2] (formerly past_local_node / send_node) is now tag[4] / tag[3]. EntanglementCounterpart and EntanglementHistory are extended at the end, so existing indices keep working there.
4. The struct constructors are backward compatible. EntanglementCounterpart(node, slot), EntanglementHistory(a, b, c, d, e), EntanglementUpdateX(a, b, c, d, e, f), and EntanglementDelete(a, b, c, d) still work and fill the new fields with NO_ENTANGLEMENT_ID. Note however that protocols match counterpart tags by exact pair ID, so hand-constructed NO_ENTANGLEMENT_ID metadata only interoperates with other legacy-ID metadata.
5. Reciprocal tags must agree on the pair ID. EntanglementConsumer (and the switch protocols) now require the two ends of a pair to carry the same pair_id in their reciprocal EntanglementCounterpart tags, not just matching (node, slot) routing info. If you create entangled pairs manually in tests or examples, tag both ends with the same ID.
6. Custom tag types are unaffected. EntanglerProt(...; tag=MyTag) keeps writing the legacy two-field MyTag(remote_node, remote_slot) schema, and EntanglementConsumer(...; tag=MyTag) keeps querying it with the legacy arity. Only EntanglementCounterpart carries a pair ID.

• (fix) Solving edge cases of deadlocks when simultaneously tagging and waiting on tags.
• Significant performance improvements to queries on registers or buffers that already contain many tags.
• New QTCP tutorial examples under examples/qtcp_tutorial/ demonstrating basic usage on a chain, GLMakie visualization, multi-flow on a grid topology, and custom endpoint controllers.

v0.6.0 - 2026-05-05

• (breaking) Some fields of EntanglerProt were renamed for consistency with other protocols. More such renaming is to be expected, for consistency's sake.
• (breaking) The StatesZoo now integrates with the Genqo.jl package, to provide high accuracy models of the ZALM entanglement source. The previous implementation of the ZALM source was removed.
• (breaking) Renaming wait(::MessageBuffer) and onchange_tag(::Register) to onchange.
• (fix) observable used to incorrectly handle subsystem permutations on some backends in some edge cases, giving wrong results.
• (fix) Stale EntanglementDelete messages in EntanglementTracker are now dropped as a workaround for protocol bookkeeping issue #303.
• (fix) Tensor products of operators are now better supported in apply! for CliffordRepr
• Querying functions now also return the time at which a tag was tagged.
• query_wait now exists as a much simpler alternative to onchange followed by query.
• GraphStateConstructor protocol and related tooling for modeling of the iterative construction of a graph state out of Bell pairs.
• Protocol constructors moving to having constructors that do not require sim to be explicitly specified.
• Noise types now have default parameters, for ease of construction in examples. The default values generally correspond to near-zero noise (e.g. decoherence time of 1e9).
• Protocols (subtypes of AbstractProtocol in the ProtocolZoo) now have rich show methods for the image/png and text/html MIME types
• Unexported function permits_virtual_edge to describe whether a protocol can run between two nodes that are not directly connected.
• Non-public functions parent, parentindex, name, namestr, timestr, compactstr, available_protocol_types, available_slot_types, available_background_types, constructor_metadata for better introspection capabilities and cleaner printing.
• T1T2 noise has been added.
• Support for Gaussian states, unitaries, and channels through GabsRepr as the default for QModes.
• HomodyneMeasurement has been added for Gaussian-state measurements.
• New assisted continuous-variable teleportation example.
• New piecemaker GHZ-switch example.
• DepolarizedBellPair added to StatesZoo, representing a depolarized Bell state p|Φ⁺⟩⟨Φ⁺| + (1-p)I/4, constructible from either the depolarization parameter p or fidelity F.

v0.5.1 - 2025-07-14

• Add classical_delay and quantum_delay as keyword arguments to the RegisterNet constructor to set a default global network edge latency.
• onchange_tag now permits a protocol to wait for any change to the tag metadata.
• Plots of networks can now overlay real-world maps (see generate_map).
• A "state explorer" tool was added to the plotting submodule and as an interactive example, to heal visualize many of the states in StatesZoo.
• Additional filtering and decision capabilities in EntanglerProt.
• Fixes and additions to available background noise processes.
• Rebuilding the ZALM source from StatesZoo in a more reproducible fashion.
• Fixes and performance improvements to observable.
• New examples related to preparing GHZ states and MBQC-based purification.
• The switch protocol is now back to fully functional, thanks to an upstream fix in GraphsMatching.jl.

v0.5.0 - 2024-10-16

• Develop CutoffProt to deal with deadlocks in a simulation
• Expand SwapperProt with agelimit to permit cutoff policies (with CutoffProt)
• Tutorial and interactive examples for entanglement distribution on a grid with local-only knowledge
• (breaking) observable now takes a default value as a kwarg, i.e., you need to make the substitution observable(regs, obs, 0.0; time) ↦ observable(regs, obs; something=0.0, time)
• Bump QuantumSymbolics and QuantumOpticsBase compat bound and bump julia compat to 1.10.
• Implement a simple switch protocol.
  • Simplify one of the switch protocols to avoid dependence on GraphsMatching.jl. which does not install well on non-linux systems. Do not rely on the default SimpleSwitchDiscreteProt for the time being.

v0.4.2 - 2024-08-13

• Incorrect breaking release. It should have been 0.5 (see above).

v0.4.1 - 2024-06-05

• Significant improvements to the performance of query.

v0.4.0 - 2024-06-03

• Establishing ProtocolZoo, CircuitZoo, and StateZoo
• Establishing Register, RegRef, and RegisterNet
• Establishing the symbolic expression capabilities
• Establishing plotting and visualization capabilities

older versions were not tracked